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David Howells authored
Fix pipe_write() to not cache the ring index mask and max_usage as their values are invalidated by calling pipe_wait() because the latter function drops the pipe lock, thereby allowing F_SETPIPE_SZ change them. Without this, pipe_write() may subsequently miscalculate the array indices and pipe fullness, leading to an oops like the following: BUG: KASAN: slab-out-of-bounds in pipe_write+0xc25/0xe10 fs/pipe.c:481 Write of size 8 at addr ffff8880771167a8 by task syz-executor.3/7987 ... CPU: 1 PID: 7987 Comm: syz-executor.3 Not tainted 5.4.0-rc2-syzkaller #0 ... Call Trace: pipe_write+0xc25/0xe10 fs/pipe.c:481 call_write_iter include/linux/fs.h:1895 [inline] new_sync_write+0x3fd/0x7e0 fs/read_write.c:483 __vfs_write+0x94/0x110 fs/read_write.c:496 vfs_write+0x18a/0x520 fs/read_write.c:558 ksys_write+0x105/0x220 fs/read_write.c:611 __do_sys_write fs/read_write.c:623 [inline] __se_sys_write fs/read_write.c:620 [inline] __x64_sys_write+0x6e/0xb0 fs/read_write.c:620 do_syscall_64+0xca/0x5d0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe This is not a problem for pipe_read() as the mask is recalculated on each pass of the loop, after pipe_wait() has been called. Fixes: 8cefc107 ("pipe: Use head and tail pointers for the ring, not cursor and length") Reported-by: syzbot+838eb0878ffd51f27c41@syzkaller.appspotmail.com Signed-off-by:
David Howells <dhowells@redhat.com> Cc: Eric Biggers <ebiggers@kernel.org> [ Changed it to use a temporary variable 'mask' to avoid long lines -Linus ] Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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