linux.git/fs, branch v5.4-rc2 Linux kernel source tree elf: don't use MAP_FIXED_NOREPLACE for elf executable mappings 2019-10-06T20:53:27+00:00 Linus Torvalds torvalds@linux-foundation.org 2019-10-06T20:53:27+00:00 b212921b13bda088a004328457c5c21458262fe2 In commit 4ed28639519c ("fs, elf: drop MAP_FIXED usage from elf_map") we changed elf to use MAP_FIXED_NOREPLACE instead of MAP_FIXED for the executable mappings. Then, people reported that it broke some binaries that had overlapping segments from the same file, and commit ad55eac74f20 ("elf: enforce MAP_FIXED on overlaying elf segments") re-instated MAP_FIXED for some overlaying elf segment cases. But only some - despite the summary line of that commit, it only did it when it also does a temporary brk vma for one obvious overlapping case. Now Russell King reports another overlapping case with old 32-bit x86 binaries, which doesn't trigger that limited case. End result: we had better just drop MAP_FIXED_NOREPLACE entirely, and go back to MAP_FIXED. Yes, it's a sign of old binaries generated with old tool-chains, but we do pride ourselves on not breaking existing setups. This still leaves MAP_FIXED_NOREPLACE in place for the load_elf_interp() and the old load_elf_library() use-cases, because nobody has reported breakage for those. Yet. Note that in all the cases seen so far, the overlapping elf sections seem to be just re-mapping of the same executable with different section attributes. We could possibly introduce a new MAP_FIXED_NOFILECHANGE flag or similar, which acts like NOREPLACE, but allows just remapping the same executable file using different protection flags. It's not clear that would make a huge difference to anything, but if people really hate that "elf remaps over previous maps" behavior, maybe at least a more limited form of remapping would alleviate some concerns. Alternatively, we should take a look at our elf_map() logic to see if we end up not mapping things properly the first time. In the meantime, this is the minimal "don't do that then" patch while people hopefully think about it more. Reported-by: Russell King <linux@armlinux.org.uk> Fixes: 4ed28639519c ("fs, elf: drop MAP_FIXED usage from elf_map") Fixes: ad55eac74f20 ("elf: enforce MAP_FIXED on overlaying elf segments") Cc: Michal Hocko <mhocko@suse.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
In commit 4ed28639519c ("fs, elf: drop MAP_FIXED usage from elf_map") we
changed elf to use MAP_FIXED_NOREPLACE instead of MAP_FIXED for the
executable mappings.

Then, people reported that it broke some binaries that had overlapping
segments from the same file, and commit ad55eac74f20 ("elf: enforce
MAP_FIXED on overlaying elf segments") re-instated MAP_FIXED for some
overlaying elf segment cases.  But only some - despite the summary line
of that commit, it only did it when it also does a temporary brk vma for
one obvious overlapping case.

Now Russell King reports another overlapping case with old 32-bit x86
binaries, which doesn't trigger that limited case.  End result: we had
better just drop MAP_FIXED_NOREPLACE entirely, and go back to MAP_FIXED.

Yes, it's a sign of old binaries generated with old tool-chains, but we
do pride ourselves on not breaking existing setups.

This still leaves MAP_FIXED_NOREPLACE in place for the load_elf_interp()
and the old load_elf_library() use-cases, because nobody has reported
breakage for those. Yet.

Note that in all the cases seen so far, the overlapping elf sections
seem to be just re-mapping of the same executable with different section
attributes.  We could possibly introduce a new MAP_FIXED_NOFILECHANGE
flag or similar, which acts like NOREPLACE, but allows just remapping
the same executable file using different protection flags.

It's not clear that would make a huge difference to anything, but if
people really hate that "elf remaps over previous maps" behavior, maybe
at least a more limited form of remapping would alleviate some concerns.

Alternatively, we should take a look at our elf_map() logic to see if we
end up not mapping things properly the first time.

In the meantime, this is the minimal "don't do that then" patch while
people hopefully think about it more.

Reported-by: Russell King <linux@armlinux.org.uk>
Fixes: 4ed28639519c ("fs, elf: drop MAP_FIXED usage from elf_map")
Fixes: ad55eac74f20 ("elf: enforce  MAP_FIXED on overlaying elf segments")
Cc: Michal Hocko <mhocko@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge branch 'readdir' (readdir speedup and sanity checking) 2019-10-05T19:03:27+00:00 Linus Torvalds torvalds@linux-foundation.org 2019-10-05T19:03:27+00:00 4f11918ab93bc113ec0831ed2ab7b88847d44dd7 This makes getdents() and getdents64() do sanity checking on the pathname that it gives to user space. And to mitigate the performance impact of that, it first cleans up the way it does the user copying, so that the code avoids doing the SMAP/PAN updates between each part of the dirent structure write. I really wanted to do this during the merge window, but didn't have time. The conversion of filldir to unsafe_put_user() is something I've had around for years now in a private branch, but the extra pathname checking finally made me clean it up to the point where it is mergable. It's worth noting that the filename validity checking really should be a bit smarter: it would be much better to delay the error reporting until the end of the readdir, so that non-corrupted filenames are still returned. But that involves bigger changes, so let's see if anybody actually hits the corrupt directory entry case before worrying about it further. * branch 'readdir': Make filldir[64]() verify the directory entry filename is valid Convert filldir[64]() from __put_user() to unsafe_put_user() 
This makes getdents() and getdents64() do sanity checking on the
pathname that it gives to user space.  And to mitigate the performance
impact of that, it first cleans up the way it does the user copying, so
that the code avoids doing the SMAP/PAN updates between each part of the
dirent structure write.

I really wanted to do this during the merge window, but didn't have
time.  The conversion of filldir to unsafe_put_user() is something I've
had around for years now in a private branch, but the extra pathname
checking finally made me clean it up to the point where it is mergable.

It's worth noting that the filename validity checking really should be a
bit smarter: it would be much better to delay the error reporting until
the end of the readdir, so that non-corrupted filenames are still
returned.  But that involves bigger changes, so let's see if anybody
actually hits the corrupt directory entry case before worrying about it
further.

* branch 'readdir':
  Make filldir[64]() verify the directory entry filename is valid
  Convert filldir[64]() from __put_user() to unsafe_put_user()
Make filldir[64]() verify the directory entry filename is valid 2019-10-05T19:00:36+00:00 Linus Torvalds torvalds@linux-foundation.org 2019-10-05T18:32:52+00:00 8a23eb804ca4f2be909e372cf5a9e7b30ae476cd This has been discussed several times, and now filesystem people are talking about doing it individually at the filesystem layer, so head that off at the pass and just do it in getdents{64}(). This is partially based on a patch by Jann Horn, but checks for NUL bytes as well, and somewhat simplified. There's also commentary about how it might be better if invalid names due to filesystem corruption don't cause an immediate failure, but only an error at the end of the readdir(), so that people can still see the filenames that are ok. There's also been discussion about just how much POSIX strictly speaking requires this since it's about filesystem corruption. It's really more "protect user space from bad behavior" as pointed out by Jann. But since Eric Biederman looked up the POSIX wording, here it is for context: "From readdir: The readdir() function shall return a pointer to a structure representing the directory entry at the current position in the directory stream specified by the argument dirp, and position the directory stream at the next entry. It shall return a null pointer upon reaching the end of the directory stream. The structure dirent defined in the <dirent.h> header describes a directory entry. From definitions: 3.129 Directory Entry (or Link) An object that associates a filename with a file. Several directory entries can associate names with the same file. ... 3.169 Filename A name consisting of 1 to {NAME_MAX} bytes used to name a file. The characters composing the name may be selected from the set of all character values excluding the slash character and the null byte. The filenames dot and dot-dot have special meaning. A filename is sometimes referred to as a 'pathname component'." Note that I didn't bother adding the checks to any legacy interfaces that nobody uses. Also note that if this ends up being noticeable as a performance regression, we can fix that to do a much more optimized model that checks for both NUL and '/' at the same time one word at a time. We haven't really tended to optimize 'memchr()', and it only checks for one pattern at a time anyway, and we really _should_ check for NUL too (but see the comment about "soft errors" in the code about why it currently only checks for '/') See the CONFIG_DCACHE_WORD_ACCESS case of hash_name() for how the name lookup code looks for pathname terminating characters in parallel. Link: https://lore.kernel.org/lkml/20190118161440.220134-2-jannh@google.com/ Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Jann Horn <jannh@google.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
This has been discussed several times, and now filesystem people are
talking about doing it individually at the filesystem layer, so head
that off at the pass and just do it in getdents{64}().

This is partially based on a patch by Jann Horn, but checks for NUL
bytes as well, and somewhat simplified.

There's also commentary about how it might be better if invalid names
due to filesystem corruption don't cause an immediate failure, but only
an error at the end of the readdir(), so that people can still see the
filenames that are ok.

There's also been discussion about just how much POSIX strictly speaking
requires this since it's about filesystem corruption.  It's really more
"protect user space from bad behavior" as pointed out by Jann.  But
since Eric Biederman looked up the POSIX wording, here it is for context:

 "From readdir:

   The readdir() function shall return a pointer to a structure
   representing the directory entry at the current position in the
   directory stream specified by the argument dirp, and position the
   directory stream at the next entry. It shall return a null pointer
   upon reaching the end of the directory stream. The structure dirent
   defined in the <dirent.h> header describes a directory entry.

  From definitions:

   3.129 Directory Entry (or Link)

   An object that associates a filename with a file. Several directory
   entries can associate names with the same file.

  ...

   3.169 Filename

   A name consisting of 1 to {NAME_MAX} bytes used to name a file. The
   characters composing the name may be selected from the set of all
   character values excluding the slash character and the null byte. The
   filenames dot and dot-dot have special meaning. A filename is
   sometimes referred to as a 'pathname component'."

Note that I didn't bother adding the checks to any legacy interfaces
that nobody uses.

Also note that if this ends up being noticeable as a performance
regression, we can fix that to do a much more optimized model that
checks for both NUL and '/' at the same time one word at a time.

We haven't really tended to optimize 'memchr()', and it only checks for
one pattern at a time anyway, and we really _should_ check for NUL too
(but see the comment about "soft errors" in the code about why it
currently only checks for '/')

See the CONFIG_DCACHE_WORD_ACCESS case of hash_name() for how the name
lookup code looks for pathname terminating characters in parallel.

Link: https://lore.kernel.org/lkml/20190118161440.220134-2-jannh@google.com/
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jann Horn <jannh@google.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Convert filldir[64]() from __put_user() to unsafe_put_user() 2019-10-05T19:00:36+00:00 Linus Torvalds torvalds@linux-foundation.org 2016-05-22T04:59:07+00:00 9f79b78ef74436c7507bac6bfb7b8b989263bccb We really should avoid the "__{get,put}_user()" functions entirely, because they can easily be mis-used and the original intent of being used for simple direct user accesses no longer holds in a post-SMAP/PAN world. Manually optimizing away the user access range check makes no sense any more, when the range check is generally much cheaper than the "enable user accesses" code that the __{get,put}_user() functions still need. So instead of __put_user(), use the unsafe_put_user() interface with user_access_{begin,end}() that really does generate better code these days, and which is generally a nicer interface. Under some loads, the multiple user writes that filldir() does are actually quite noticeable. This also makes the dirent name copy use unsafe_put_user() with a couple of macros. We do not want to make function calls with SMAP/PAN disabled, and the code this generates is quite good when the architecture uses "asm goto" for unsafe_put_user() like x86 does. Note that this doesn't bother with the legacy cases. Nobody should use them anyway, so performance doesn't really matter there. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
We really should avoid the "__{get,put}_user()" functions entirely,
because they can easily be mis-used and the original intent of being
used for simple direct user accesses no longer holds in a post-SMAP/PAN
world.

Manually optimizing away the user access range check makes no sense any
more, when the range check is generally much cheaper than the "enable
user accesses" code that the __{get,put}_user() functions still need.

So instead of __put_user(), use the unsafe_put_user() interface with
user_access_{begin,end}() that really does generate better code these
days, and which is generally a nicer interface.  Under some loads, the
multiple user writes that filldir() does are actually quite noticeable.

This also makes the dirent name copy use unsafe_put_user() with a couple
of macros.  We do not want to make function calls with SMAP/PAN
disabled, and the code this generates is quite good when the
architecture uses "asm goto" for unsafe_put_user() like x86 does.

Note that this doesn't bother with the legacy cases.  Nobody should use
them anyway, so performance doesn't really matter there.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge tag 'for-linus-2019-10-03' of git://git.kernel.dk/linux-block 2019-10-04T16:56:51+00:00 Linus Torvalds torvalds@linux-foundation.org 2019-10-04T16:56:51+00:00 c4bd70e8c95b2b045ac686b4c654bf9bfbfe9f3b Pull block fixes from Jens Axboe: - Mandate timespec64 for the io_uring timeout ABI (Arnd) - Set of NVMe changes via Sagi: - controller removal race fix from Balbir - quirk additions from Gabriel and Jian-Hong - nvme-pci power state save fix from Mario - Add 64bit user commands (for 64bit registers) from Marta - nvme-rdma/nvme-tcp fixes from Max, Mark and Me - Minor cleanups and nits from James, Dan and John - Two s390 dasd fixes (Jan, Stefan) - Have loop change block size in DIO mode (Martijn) - paride pg header ifdef guard (Masahiro) - Two blk-mq queue scheduler tweaks, fixing an ordering issue on zoned devices and suboptimal performance on others (Ming) * tag 'for-linus-2019-10-03' of git://git.kernel.dk/linux-block: (22 commits) block: sed-opal: fix sparse warning: convert __be64 data block: sed-opal: fix sparse warning: obsolete array init. block: pg: add header include guard Revert "s390/dasd: Add discard support for ESE volumes" s390/dasd: Fix error handling during online processing io_uring: use __kernel_timespec in timeout ABI loop: change queue block size to match when using DIO blk-mq: apply normal plugging for HDD blk-mq: honor IO scheduler for multiqueue devices nvme-rdma: fix possible use-after-free in connect timeout nvme: Move ctrl sqsize to generic space nvme: Add ctrl attributes for queue_count and sqsize nvme: allow 64-bit results in passthru commands nvme: Add quirk for Kingston NVME SSD running FW E8FK11.T nvmet-tcp: remove superflous check on request sgl Added QUIRKs for ADATA XPG SX8200 Pro 512GB nvme-rdma: Fix max_hw_sectors calculation nvme: fix an error code in nvme_init_subsystem() nvme-pci: Save PCI state before putting drive into deepest state nvme-tcp: fix wrong stop condition in io_work ... 
Pull block fixes from Jens Axboe:

 - Mandate timespec64 for the io_uring timeout ABI (Arnd)

 - Set of NVMe changes via Sagi:
     - controller removal race fix from Balbir
     - quirk additions from Gabriel and Jian-Hong
     - nvme-pci power state save fix from Mario
     - Add 64bit user commands (for 64bit registers) from Marta
     - nvme-rdma/nvme-tcp fixes from Max, Mark and Me
     - Minor cleanups and nits from James, Dan and John

 - Two s390 dasd fixes (Jan, Stefan)

 - Have loop change block size in DIO mode (Martijn)

 - paride pg header ifdef guard (Masahiro)

 - Two blk-mq queue scheduler tweaks, fixing an ordering issue on zoned
   devices and suboptimal performance on others (Ming)

* tag 'for-linus-2019-10-03' of git://git.kernel.dk/linux-block: (22 commits)
  block: sed-opal: fix sparse warning: convert __be64 data
  block: sed-opal: fix sparse warning: obsolete array init.
  block: pg: add header include guard
  Revert "s390/dasd: Add discard support for ESE volumes"
  s390/dasd: Fix error handling during online processing
  io_uring: use __kernel_timespec in timeout ABI
  loop: change queue block size to match when using DIO
  blk-mq: apply normal plugging for HDD
  blk-mq: honor IO scheduler for multiqueue devices
  nvme-rdma: fix possible use-after-free in connect timeout
  nvme: Move ctrl sqsize to generic space
  nvme: Add ctrl attributes for queue_count and sqsize
  nvme: allow 64-bit results in passthru commands
  nvme: Add quirk for Kingston NVME SSD running FW E8FK11.T
  nvmet-tcp: remove superflous check on request sgl
  Added QUIRKs for ADATA XPG SX8200 Pro 512GB
  nvme-rdma: Fix max_hw_sectors calculation
  nvme: fix an error code in nvme_init_subsystem()
  nvme-pci: Save PCI state before putting drive into deepest state
  nvme-tcp: fix wrong stop condition in io_work
  ...
vfs: Fix EOVERFLOW testing in put_compat_statfs64 2019-10-03T21:21:35+00:00 Eric Sandeen sandeen@redhat.com 2019-10-02T21:17:54+00:00 cc3a7bfe62b947b423fcb2cfe89fcba92bf48fa3 Today, put_compat_statfs64() disallows nearly any field value over 2^32 if f_bsize is only 32 bits, but that makes no sense. compat_statfs64 is there for the explicit purpose of providing 64-bit fields for f_files, f_ffree, etc. And f_bsize is always only 32 bits. As a result, 32-bit userspace gets -EOVERFLOW for i.e. large file counts even with -D_FILE_OFFSET_BITS=64 set. In reality, only f_bsize and f_frsize can legitimately overflow (fields like f_type and f_namelen should never be large), so test only those fields. This bug was discussed at length some time ago, and this is the proposal Al suggested at https://lkml.org/lkml/2018/8/6/640. It seemed to get dropped amid the discussion of other related changes, but this part seems obviously correct on its own, so I've picked it up and sent it, for expediency. Fixes: 64d2ab32efe3 ("vfs: fix put_compat_statfs64() does not handle errors") Signed-off-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
Today, put_compat_statfs64() disallows nearly any field value over
2^32 if f_bsize is only 32 bits, but that makes no sense.
compat_statfs64 is there for the explicit purpose of providing 64-bit
fields for f_files, f_ffree, etc.  And f_bsize is always only 32 bits.

As a result, 32-bit userspace gets -EOVERFLOW for i.e.  large file
counts even with -D_FILE_OFFSET_BITS=64 set.

In reality, only f_bsize and f_frsize can legitimately overflow
(fields like f_type and f_namelen should never be large), so test
only those fields.

This bug was discussed at length some time ago, and this is the proposal
Al suggested at https://lkml.org/lkml/2018/8/6/640.  It seemed to get
dropped amid the discussion of other related changes, but this
part seems obviously correct on its own, so I've picked it up and
sent it, for expediency.

Fixes: 64d2ab32efe3 ("vfs: fix put_compat_statfs64() does not handle errors")
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
io_uring: use __kernel_timespec in timeout ABI 2019-10-01T15:53:29+00:00 Arnd Bergmann arnd@arndb.de 2019-10-01T15:53:29+00:00 bdf200731145f07a6127cb16753e2e8fdc159cf4 All system calls use struct __kernel_timespec instead of the old struct timespec, but this one was just added with the old-style ABI. Change it now to enforce the use of __kernel_timespec, avoiding ABI confusion and the need for compat handlers on 32-bit architectures. Any user space caller will have to use __kernel_timespec now, but this is unambiguous and works for any C library regardless of the time_t definition. A nicer way to specify the timeout would have been a less ambiguous 64-bit nanosecond value, but I suppose it's too late now to change that as this would impact both 32-bit and 64-bit users. Fixes: 5262f567987d ("io_uring: IORING_OP_TIMEOUT support") Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
All system calls use struct __kernel_timespec instead of the old struct
timespec, but this one was just added with the old-style ABI. Change it
now to enforce the use of __kernel_timespec, avoiding ABI confusion and
the need for compat handlers on 32-bit architectures.

Any user space caller will have to use __kernel_timespec now, but this
is unambiguous and works for any C library regardless of the time_t
definition. A nicer way to specify the timeout would have been a less
ambiguous 64-bit nanosecond value, but I suppose it's too late now to
change that as this would impact both 32-bit and 64-bit users.

Fixes: 5262f567987d ("io_uring: IORING_OP_TIMEOUT support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
erofs: fix mis-inplace determination related with noio chain 2019-09-30T20:54:45+00:00 Gao Xiang gaoxiang25@huawei.com 2019-09-22T10:04:34+00:00 dc76ea8c1087b5c44235566ed4be2202d21a8504 Fix a recent cleanup patch. noio (bypass) chain is handled asynchronously against submit chain, therefore inplace I/O or pagevec cannot be applied to such pages. Add detailed comment for this as well. Fixes: 97e86a858bc3 ("staging: erofs: tidy up decompression frontend") Reviewed-by: Chao Yu <yuchao0@huawei.com> Link: https://lore.kernel.org/r/20190922100434.229340-1-gaoxiang25@huawei.com Signed-off-by: Gao Xiang <gaoxiang25@huawei.com> 
Fix a recent cleanup patch. noio (bypass) chain is
handled asynchronously against submit chain, therefore
inplace I/O or pagevec cannot be applied to such pages.
Add detailed comment for this as well.

Fixes: 97e86a858bc3 ("staging: erofs: tidy up decompression frontend")
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190922100434.229340-1-gaoxiang25@huawei.com
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
erofs: fix erofs_get_meta_page locking due to a cleanup 2019-09-30T20:54:33+00:00 Gao Xiang gaoxiang25@huawei.com 2019-09-21T18:43:55+00:00 55252ab72b774119afedfdc6d1f142ffa2a9b818 After doing more drop_caches stress test on our products, I found the mistake introduced by a very recent cleanup [1]. The current rule is that "erofs_get_meta_page" should be returned with page locked (although it's mostly unnecessary for read-only fs after pages are PG_uptodate), but a fix should be done for this. [1] https://lore.kernel.org/r/20190904020912.63925-26-gaoxiang25@huawei.com Fixes: 618f40ea026b ("erofs: use read_cache_page_gfp for erofs_get_meta_page") Reviewed-by: Chao Yu <yuchao0@huawei.com> Link: https://lore.kernel.org/r/20190921184355.149928-1-gaoxiang25@huawei.com Signed-off-by: Gao Xiang <gaoxiang25@huawei.com> 
After doing more drop_caches stress test on
our products, I found the mistake introduced by
a very recent cleanup [1].

The current rule is that "erofs_get_meta_page"
should be returned with page locked (although
it's mostly unnecessary for read-only fs after
pages are PG_uptodate), but a fix should be
done for this.

[1] https://lore.kernel.org/r/20190904020912.63925-26-gaoxiang25@huawei.com
Fixes: 618f40ea026b ("erofs: use read_cache_page_gfp for erofs_get_meta_page")
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190921184355.149928-1-gaoxiang25@huawei.com
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
erofs: fix return value check in erofs_read_superblock() 2019-09-30T20:53:50+00:00 Wei Yongjun weiyongjun1@huawei.com 2019-09-18T08:30:33+00:00 517d6b9c6f71bee15c729155445c42cc4ef77dda In case of error, the function read_mapping_page() returns ERR_PTR() not NULL. The NULL test in the return value check should be replaced with IS_ERR(). Fixes: fe7c2423570d ("erofs: use read_mapping_page instead of sb_bread") Reviewed-by: Gao Xiang <gaoxiang25@huawei.com> Reviewed-by: Chao Yu <yuchao0@huawei.com> Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com> Link: https://lore.kernel.org/r/20190918083033.47780-1-weiyongjun1@huawei.com Signed-off-by: Gao Xiang <gaoxiang25@huawei.com> 
In case of error, the function read_mapping_page() returns
ERR_PTR() not NULL. The NULL test in the return value check
should be replaced with IS_ERR().

Fixes: fe7c2423570d ("erofs: use read_mapping_page instead of sb_bread")
Reviewed-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20190918083033.47780-1-weiyongjun1@huawei.com
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>