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authorLai Jiangshan <laijs@cn.fujitsu.com>2014-06-06 14:37:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-06 16:08:12 -0700
commitaef0f62e87122c0fb90d5da660fd131acd0a9d67 (patch)
treed540031839fa4841b5e73a339beacd56c612baba /lib
parent8f9f665a707721146f24a892b1a0da1ab4da1d58 (diff)
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idr: fix NULL pointer dereference when ida_remove(unallocated_id)
If the ida has at least one existing id, and when an unallocated ID which meets a certain condition is passed to the ida_remove(), the system will crash because it hits NULL pointer dereference. The condition is that the unallocated ID shares the same lowest idr layer with the existing ID, but the idr slot would be different if the unallocated ID were to be allocated. In this case the matching idr slot for the unallocated_id is NULL, causing @bitmap to be NULL which the function dereferences without checking crashing the kernel. See the test code: static void test3(void) { int id; DEFINE_IDA(test_ida); printk(KERN_INFO "Start test3\n"); if (ida_pre_get(&test_ida, GFP_KERNEL) < 0) return; if (ida_get_new(&test_ida, &id) < 0) return; ida_remove(&test_ida, 4000); /* bug: null deference here */ printk(KERN_INFO "End of test3\n"); } It happens only when the caller tries to free an unallocated ID which is the caller's fault. It is not a bug. But it is better to add the proper check and complain rather than crashing the kernel. [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>
Diffstat (limited to 'lib')
-rw-r--r--lib/idr.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/lib/idr.c b/lib/idr.c
index c4afd94bdf69..36ff732fd2a6 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -1048,7 +1048,7 @@ void ida_remove(struct ida *ida, int id)
__clear_bit(n, p->bitmap);
bitmap = (void *)p->ary[n];
- if (!test_bit(offset, bitmap->bitmap))
+ if (!bitmap || !test_bit(offset, bitmap->bitmap))
goto err;
/* update bitmap and remove it if empty */