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author | Lai Jiangshan <laijs@cn.fujitsu.com> | 2014-06-06 14:37:10 -0700 |
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committer | Jiri Slaby <jslaby@suse.cz> | 2014-07-02 12:06:14 +0200 |
commit | 09b6ffbba999d9640bb32f2ccf46e883f232e833 (patch) | |
tree | 599ebcf73a5ddfb71a9aa7ab03c0d4ae53b66441 /lib | |
parent | 177ee132eb7a7209e188c5d77584eedea840a01a (diff) | |
download | lwn-09b6ffbba999d9640bb32f2ccf46e883f232e833.tar.gz lwn-09b6ffbba999d9640bb32f2ccf46e883f232e833.zip |
idr: fix overflow bug during maximum ID calculation at maximum height
commit 3afb69cb5572b3c8c898c00880803cf1a49852c4 upstream.
idr_replace() open-codes the logic to calculate the maximum valid ID
given the height of the idr tree; unfortunately, the open-coded logic
doesn't account for the fact that the top layer may have unused slots
and over-shifts the limit to zero when the tree is at its maximum
height.
The following test code shows it fails to replace the value for
id=((1<<27)+42):
static void test5(void)
{
int id;
DEFINE_IDR(test_idr);
#define TEST5_START ((1<<27)+42) /* use the highest layer */
printk(KERN_INFO "Start test5\n");
id = idr_alloc(&test_idr, (void *)1, TEST5_START, 0, GFP_KERNEL);
BUG_ON(id != TEST5_START);
TEST_BUG_ON(idr_replace(&test_idr, (void *)2, TEST5_START) != (void *)1);
idr_destroy(&test_idr);
printk(KERN_INFO "End of test5\n");
}
Fix the bug by using idr_max() which correctly takes into account the
maximum allowed shift.
sub_alloc() shares the same problem and may incorrectly fail with
-EAGAIN; however, this bug doesn't affect correct operation because
idr_get_empty_slot(), which already uses idr_max(), retries with the
increased @id in such cases.
[tj@kernel.org: Updated patch description.]
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Diffstat (limited to 'lib')
-rw-r--r-- | lib/idr.c | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/lib/idr.c b/lib/idr.c index bfe4db4e165f..674c30bc2ed0 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -250,7 +250,7 @@ static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa, id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1; /* if already at the top layer, we need to grow */ - if (id >= 1 << (idp->layers * IDR_BITS)) { + if (id > idr_max(idp->layers)) { *starting_id = id; return -EAGAIN; } @@ -827,12 +827,10 @@ void *idr_replace(struct idr *idp, void *ptr, int id) if (!p) return ERR_PTR(-EINVAL); - n = (p->layer+1) * IDR_BITS; - - if (id >= (1 << n)) + if (id > idr_max(p->layer + 1)) return ERR_PTR(-EINVAL); - n -= IDR_BITS; + n = p->layer * IDR_BITS; while ((n > 0) && p) { p = p->ary[(id >> n) & IDR_MASK]; n -= IDR_BITS; |