pipe: avoid round_pipe_size() nr_pages overflow on 32-bit
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>
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17
fs/pipe.c
17
fs/pipe.c
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@ -1018,13 +1018,19 @@ const struct file_operations pipefifo_fops = {
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/*
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/*
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* Currently we rely on the pipe array holding a power-of-2 number
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* Currently we rely on the pipe array holding a power-of-2 number
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* of pages.
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* of pages. Returns 0 on error.
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*/
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*/
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static inline unsigned int round_pipe_size(unsigned int size)
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static inline unsigned int round_pipe_size(unsigned int size)
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{
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{
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unsigned long nr_pages;
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unsigned long nr_pages;
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if (size < pipe_min_size)
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size = pipe_min_size;
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nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
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nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
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if (nr_pages == 0)
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return 0;
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return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
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return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
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}
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}
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@ -1040,6 +1046,8 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
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long ret = 0;
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long ret = 0;
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size = round_pipe_size(arg);
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size = round_pipe_size(arg);
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if (size == 0)
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return -EINVAL;
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nr_pages = size >> PAGE_SHIFT;
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nr_pages = size >> PAGE_SHIFT;
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if (!nr_pages)
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if (!nr_pages)
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@ -1123,13 +1131,18 @@ out_revert_acct:
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int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
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int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
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size_t *lenp, loff_t *ppos)
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size_t *lenp, loff_t *ppos)
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{
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{
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unsigned int rounded_pipe_max_size;
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int ret;
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int ret;
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ret = proc_douintvec_minmax(table, write, buf, lenp, ppos);
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ret = proc_douintvec_minmax(table, write, buf, lenp, ppos);
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if (ret < 0 || !write)
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if (ret < 0 || !write)
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return ret;
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return ret;
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pipe_max_size = round_pipe_size(pipe_max_size);
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rounded_pipe_max_size = round_pipe_size(pipe_max_size);
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if (rounded_pipe_max_size == 0)
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return -EINVAL;
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pipe_max_size = rounded_pipe_max_size;
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return ret;
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return ret;
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}
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}
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