The patch titled
Subject: pipe: avoid round_pipe_size() nr_pages overflow on 32-bit
has been added to the -mm tree. Its filename is
pipe-avoid-round_pipe_size-nr_pages-overflow-on-32-bit.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/pipe-avoid-round_pipe_size-nr_pages-overflow-on-32-bit.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/pipe-avoid-round_pipe_size-nr_pages-overflow-on-32-bit.patch
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------------------------------------------------------
From: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx
Signed-off-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
Reported-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Reviewed-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/pipe.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
diff -puN fs/pipe.c~pipe-avoid-round_pipe_size-nr_pages-overflow-on-32-bit fs/pipe.c
--- a/fs/pipe.c~pipe-avoid-round_pipe_size-nr_pages-overflow-on-32-bit
+++ a/fs/pipe.c
@@ -1017,13 +1017,19 @@ const struct file_operations pipefifo_fo
/*
* 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;
}
@@ -1039,6 +1045,8 @@ static long pipe_set_size(struct pipe_in
long ret = 0;
size = round_pipe_size(arg);
+ if (size == 0)
+ return -EINVAL;
nr_pages = size >> PAGE_SHIFT;
if (!nr_pages)
@@ -1122,13 +1130,18 @@ out_revert_acct:
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_douintvec_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;
}
_
Patches currently in -mm which might be from joe.lawrence@xxxxxxxxxx are
pipe-match-pipe_max_size-data-type-with-procfs.patch
pipe-avoid-round_pipe_size-nr_pages-overflow-on-32-bit.patch
pipe-add-proc_dopipe_max_size-to-safely-assign-pipe_max_size.patch
sysctl-check-for-uint_max-before-unsigned-int-min-max.patch
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