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authorDarrick J. Wong <darrick.wong@oracle.com>2019-02-13 11:15:17 -0800
committerDarrick J. Wong <darrick.wong@oracle.com>2019-02-14 09:36:52 -0800
commit3b50086f0c0d78c144d9483fa292c1509c931b70 (patch)
tree8691f3942583f0e06a09a942271f58711c8244fc /fs/xfs/xfs_attr_list.c
parent670105de15cd98f0ad6e34464c720cf9c96f4e6e (diff)
xfs: don't overflow xattr listent buffer
For VFS listxattr calls, xfs_xattr_put_listent calls __xfs_xattr_put_listent twice if it sees an attribute "trusted.SGI_ACL_FILE": once for that name, and again for "system.posix_acl_access". Unfortunately, if we happen to run out of buffer space while emitting the first name, we set count to -1 (so that we can feed ERANGE to the caller). The second invocation doesn't check that the context parameters make sense and overwrites the byte before the buffer, triggering a KASAN report: ================================================================== BUG: KASAN: slab-out-of-bounds in strncpy+0xb3/0xd0 Write of size 1 at addr ffff88807fbd317f by task syz/1113 CPU: 3 PID: 1113 Comm: syz Not tainted 5.0.0-rc6-xfsx #rc6 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-1ubuntu1 04/01/2014 Call Trace: dump_stack+0xcc/0x180 print_address_description+0x6c/0x23c kasan_report.cold.3+0x1c/0x35 strncpy+0xb3/0xd0 __xfs_xattr_put_listent+0x1a9/0x2c0 [xfs] xfs_attr_list_int_ilocked+0x11af/0x1800 [xfs] xfs_attr_list_int+0x20c/0x2e0 [xfs] xfs_vn_listxattr+0x225/0x320 [xfs] listxattr+0x11f/0x1b0 path_listxattr+0xbd/0x130 do_syscall_64+0x139/0x560 While we're at it we add an assert to the other put_listent to avoid this sort of thing ever happening to the attrlist_by_handle code. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'fs/xfs/xfs_attr_list.c')
-rw-r--r--fs/xfs/xfs_attr_list.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/xfs/xfs_attr_list.c b/fs/xfs/xfs_attr_list.c
index a58034049995..3d213a7394c5 100644
--- a/fs/xfs/xfs_attr_list.c
+++ b/fs/xfs/xfs_attr_list.c
@@ -555,6 +555,7 @@ xfs_attr_put_listent(
attrlist_ent_t *aep;
int arraytop;
+ ASSERT(!context->seen_enough);
ASSERT(!(context->flags & ATTR_KERNOVAL));
ASSERT(context->count >= 0);
ASSERT(context->count < (ATTR_MAX_VALUELEN/8));