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authorDavid Howells <dhowells@redhat.com>2022-03-11 13:23:31 +0000
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-11 10:17:12 -0800
commitc993ee0f9f81caf5767a50d1faeba39a0dc82af2 (patch)
treec1499776a143dcf141724e0f9b01996ad06af230
parentffb217a13a2eaf6d5bd974fc83036a53ca69f1e2 (diff)
watch_queue: Fix filter limit check
In watch_queue_set_filter(), there are a couple of places where we check that the filter type value does not exceed what the type_filter bitmap can hold. One place calculates the number of bits by: if (tf[i].type >= sizeof(wfilter->type_filter) * 8) which is fine, but the second does: if (tf[i].type >= sizeof(wfilter->type_filter) * BITS_PER_LONG) which is not. This can lead to a couple of out-of-bounds writes due to a too-large type: (1) __set_bit() on wfilter->type_filter (2) Writing more elements in wfilter->filters[] than we allocated. Fix this by just using the proper WATCH_TYPE__NR instead, which is the number of types we actually know about. The bug may cause an oops looking something like: BUG: KASAN: slab-out-of-bounds in watch_queue_set_filter+0x659/0x740 Write of size 4 at addr ffff88800d2c66bc by task watch_queue_oob/611 ... Call Trace: <TASK> dump_stack_lvl+0x45/0x59 print_address_description.constprop.0+0x1f/0x150 ... kasan_report.cold+0x7f/0x11b ... watch_queue_set_filter+0x659/0x740 ... __x64_sys_ioctl+0x127/0x190 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae Allocated by task 611: kasan_save_stack+0x1e/0x40 __kasan_kmalloc+0x81/0xa0 watch_queue_set_filter+0x23a/0x740 __x64_sys_ioctl+0x127/0x190 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae The buggy address belongs to the object at ffff88800d2c66a0 which belongs to the cache kmalloc-32 of size 32 The buggy address is located 28 bytes inside of 32-byte region [ffff88800d2c66a0, ffff88800d2c66c0) Fixes: c73be61cede5 ("pipe: Add general notification queue support") Reported-by: Jann Horn <jannh@google.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/watch_queue.h3
-rw-r--r--kernel/watch_queue.c4
2 files changed, 4 insertions, 3 deletions
diff --git a/include/linux/watch_queue.h b/include/linux/watch_queue.h
index c994d1b2cdba..3b9a40ae8bdb 100644
--- a/include/linux/watch_queue.h
+++ b/include/linux/watch_queue.h
@@ -28,7 +28,8 @@ struct watch_type_filter {
struct watch_filter {
union {
struct rcu_head rcu;
- unsigned long type_filter[2]; /* Bitmask of accepted types */
+ /* Bitmask of accepted types */
+ DECLARE_BITMAP(type_filter, WATCH_TYPE__NR);
};
u32 nr_filters; /* Number of filters */
struct watch_type_filter filters[];
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index 9c9eb20dd2c5..427b0318e303 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -320,7 +320,7 @@ long watch_queue_set_filter(struct pipe_inode_info *pipe,
tf[i].info_mask & WATCH_INFO_LENGTH)
goto err_filter;
/* Ignore any unknown types */
- if (tf[i].type >= sizeof(wfilter->type_filter) * 8)
+ if (tf[i].type >= WATCH_TYPE__NR)
continue;
nr_filter++;
}
@@ -336,7 +336,7 @@ long watch_queue_set_filter(struct pipe_inode_info *pipe,
q = wfilter->filters;
for (i = 0; i < filter.nr_filters; i++) {
- if (tf[i].type >= sizeof(wfilter->type_filter) * BITS_PER_LONG)
+ if (tf[i].type >= WATCH_TYPE__NR)
continue;
q->type = tf[i].type;