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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2022-03-29 23:29:18 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-03-29 23:29:18 -0700 |
| commit | d888c83fcec75194a8a48ccd283953bdba7b2550 (patch) | |
| tree | 66c5fd5d83bb02fcfbb678191ae34edbe0c4904d /fs/file.c | |
| parent | 965181d7ef7e1a863477536dc328c23a7ebc8a1d (diff) | |
| download | lwn-d888c83fcec75194a8a48ccd283953bdba7b2550.tar.gz lwn-d888c83fcec75194a8a48ccd283953bdba7b2550.zip | |
fs: fix fd table size alignment properly
Jason Donenfeld reports that my commit 1c24a186398f ("fs: fd tables have
to be multiples of BITS_PER_LONG") doesn't work, and the reason is an
embarrassing brown-paper-bag bug.
Yes, we want to align the number of fds to BITS_PER_LONG, and yes, the
reason they might not be aligned is because the incoming 'max_fd'
argument might not be aligned.
But aligining the argument - while simple - will cause a "infinitely
big" maxfd (eg NR_OPEN_MAX) to just overflow to zero. Which most
definitely isn't what we want either.
The obvious fix was always just to do the alignment last, but I had
moved it earlier just to make the patch smaller and the code look
simpler. Duh. It certainly made _me_ look simple.
Fixes: 1c24a186398f ("fs: fd tables have to be multiples of BITS_PER_LONG")
Reported-and-tested-by: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Fedor Pchelkin <aissur0002@gmail.com>
Cc: Alexey Khoroshilov <khoroshilov@ispras.ru>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/file.c')
| -rw-r--r-- | fs/file.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/fs/file.c b/fs/file.c index c01c29417ae6..ee9317346702 100644 --- a/fs/file.c +++ b/fs/file.c @@ -303,10 +303,9 @@ static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds) unsigned int count; count = count_open_files(fdt); - max_fds = ALIGN(max_fds, BITS_PER_LONG); if (max_fds < NR_OPEN_DEFAULT) max_fds = NR_OPEN_DEFAULT; - return min(count, max_fds); + return ALIGN(min(count, max_fds), BITS_PER_LONG); } /* |