[PATCH] afs: Set vllist to NULL if addr parsing fails
David Howells
dhowells at redhat.com
Mon Jul 21 07:26:51 PDT 2025
From: Edward Adam Davis <eadavis at qq.com>
syzbot reported a bug in in afs_put_vlserverlist.
kAFS: bad VL server IP address
BUG: unable to handle page fault for address: fffffffffffffffa
...
Oops: Oops: 0002 [#1] SMP KASAN PTI
...
RIP: 0010:refcount_dec_and_test include/linux/refcount.h:450 [inline]
RIP: 0010:afs_put_vlserverlist+0x3a/0x220 fs/afs/vl_list.c:67
...
Call Trace:
<TASK>
afs_alloc_cell fs/afs/cell.c:218 [inline]
afs_lookup_cell+0x12a5/0x1680 fs/afs/cell.c:264
afs_cell_init+0x17a/0x380 fs/afs/cell.c:386
afs_proc_rootcell_write+0x21f/0x290 fs/afs/proc.c:247
proc_simple_write+0x114/0x1b0 fs/proc/generic.c:825
pde_write fs/proc/inode.c:330 [inline]
proc_reg_write+0x23d/0x330 fs/proc/inode.c:342
vfs_write+0x25c/0x1180 fs/read_write.c:682
ksys_write+0x12a/0x240 fs/read_write.c:736
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Because afs_parse_text_addrs() parses incorrectly, its return value -EINVAL
is assigned to vllist, which results in -EINVAL being used as the vllist
address when afs_put_vlserverlist() is executed.
Set the vllist value to NULL when a parsing error occurs to avoid this
issue.
Fixes: e2c2cb8ef07a ("afs: Simplify cell record handling")
Reported-by: syzbot+5c042fbab0b292c98fc6 at syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=5c042fbab0b292c98fc6
Tested-by: syzbot+5c042fbab0b292c98fc6 at syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis at qq.com>
Signed-off-by: David Howells <dhowells at redhat.com>
cc: Marc Dionne <marc.dionne at auristor.com>
cc: linux-afs at lists.infradead.org
cc: linux-fsdevel at vger.kernel.org
---
fs/afs/cell.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index 0168bbf53fe0..f31359922e98 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -177,6 +177,7 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
VL_SERVICE, AFS_VL_PORT);
if (IS_ERR(vllist)) {
ret = PTR_ERR(vllist);
+ vllist = NULL;
goto parse_failed;
}
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