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author | Joe Lawrence <joe.lawrence@redhat.com> | 2017-11-18 02:29:21 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-01-23 21:50:15 +0300 |
commit | aa041f13f8c6761ba985a4aab42c0dab49ec4202 (patch) | |
tree | 7ad2ddc96c0920d97753e677d65cbec62e931f3c /fs/pipe.c | |
parent | 1782af2835fe6fbff6265a53fb85847fb9c58137 (diff) | |
download | linux-aa041f13f8c6761ba985a4aab42c0dab49ec4202.tar.xz |
pipe: avoid round_pipe_size() nr_pages overflow on 32-bit
commit d3f14c485867cfb2e0c48aa88c41d0ef4bf5209c upstream.
round_pipe_size() contains a right-bit-shift expression which may
overflow, which would cause undefined results in a subsequent
roundup_pow_of_two() call.
static inline unsigned int round_pipe_size(unsigned int size)
{
unsigned long nr_pages;
nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
}
PAGE_SIZE is defined as (1UL << PAGE_SHIFT), so:
- 4 bytes wide on 32-bit (0 to 0xffffffff)
- 8 bytes wide on 64-bit (0 to 0xffffffffffffffff)
That means that 32-bit round_pipe_size(), nr_pages may overflow to 0:
size=0x00000000 nr_pages=0x0
size=0x00000001 nr_pages=0x1
size=0xfffff000 nr_pages=0xfffff
size=0xfffff001 nr_pages=0x0 << !
size=0xffffffff nr_pages=0x0 << !
This is bad because roundup_pow_of_two(n) is undefined when n == 0!
64-bit is not a problem as the unsigned int size is 4 bytes wide
(similar to 32-bit) and the larger, 8 byte wide unsigned long, is
sufficient to handle the largest value of the bit shift expression:
size=0xffffffff nr_pages=100000
Modify round_pipe_size() to return 0 if n == 0 and updates its callers to
handle accordingly.
Link: http://lkml.kernel.org/r/1507658689-11669-3-git-send-email-joe.lawrence@redhat.com
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dong Jinguang <dongjinguang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/pipe.c')
-rw-r--r-- | fs/pipe.c | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index ab8dad3ccb6a..39eff9a67253 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -1001,6 +1001,9 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages) { struct pipe_buffer *bufs; + if (!nr_pages) + return -EINVAL; + /* * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't * expect a lot of shrink+grow operations, just free and allocate @@ -1045,13 +1048,19 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages) /* * Currently we rely on the pipe array holding a power-of-2 number - * of pages. + * of pages. Returns 0 on error. */ static inline unsigned int round_pipe_size(unsigned int size) { unsigned long nr_pages; + if (size < pipe_min_size) + size = pipe_min_size; + nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (nr_pages == 0) + return 0; + return roundup_pow_of_two(nr_pages) << PAGE_SHIFT; } @@ -1062,13 +1071,18 @@ static inline unsigned int round_pipe_size(unsigned int size) int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf, size_t *lenp, loff_t *ppos) { + unsigned int rounded_pipe_max_size; int ret; ret = proc_dointvec_minmax(table, write, buf, lenp, ppos); if (ret < 0 || !write) return ret; - pipe_max_size = round_pipe_size(pipe_max_size); + rounded_pipe_max_size = round_pipe_size(pipe_max_size); + if (rounded_pipe_max_size == 0) + return -EINVAL; + + pipe_max_size = rounded_pipe_max_size; return ret; } |