From: Joe Lawrence Date: Fri, 17 Nov 2017 23:29:21 +0000 (-0800) Subject: pipe: avoid round_pipe_size() nr_pages overflow on 32-bit X-Git-Tag: v3.18.93~43 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d3c49810dc8d90bcff410c4e635ef817af2b2fc1;p=thirdparty%2Fkernel%2Fstable.git 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 Reported-by: Mikulas Patocka Reviewed-by: Mikulas Patocka Cc: Al Viro Cc: Jens Axboe Cc: Michael Kerrisk Cc: Randy Dunlap Cc: Josh Poimboeuf Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Dong Jinguang Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/pipe.c b/fs/pipe.c index e3ba6c3a17430..a0cb84474fceb 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -1002,6 +1002,9 @@ 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 @@ -1046,13 +1049,19 @@ 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; } @@ -1063,13 +1072,18 @@ 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; }