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afs: Fix memory leak when mounting with multiple source parameters 

There's a memory leak in afs_parse_source() whereby multiple source=
parameters overwrite fc->source in the fs_context struct without freeing
the previously recorded source.

Fix this by only permitting a single source parameter and rejecting with
an error all subsequent ones.

This was caught by syzbot with the kernel memory leak detector, showing
something like the following trace:

  unreferenced object 0xffff888114375440 (size 32):
    comm "repro", pid 5168, jiffies 4294923723 (age 569.948s)
    backtrace:
      slab_post_alloc_hook+0x42/0x79
      __kmalloc_track_caller+0x125/0x16a
      kmemdup_nul+0x24/0x3c
      vfs_parse_fs_string+0x5a/0xa1
      generic_parse_monolithic+0x9d/0xc5
      do_new_mount+0x10d/0x15a
      do_mount+0x5f/0x8e
      __do_sys_mount+0xff/0x127
      do_syscall_64+0x2d/0x3a
      entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: 13fcc68370 ("afs: Add fs_context support")
Reported-by: syzbot+86dc6632faaca40133ab@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Howells 2020-12-08 23:52:03 +00:00 committed by Linus Torvalds
parent c6f7e1510b
commit 4cb6829647
1 changed files with 3 additions and 0 deletions
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3
fs/afs/super.c
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@ -230,6 +230,9 @@ static int afs_parse_source(struct fs_context *fc, struct fs_parameter *param)
_enter(",%s", name); _enter(",%s", name);
if (fc->source)
return invalf(fc, "kAFS: Multiple sources not supported");
if (!name) { if (!name) {
printk(KERN_ERR "kAFS: no volume name specified\n"); printk(KERN_ERR "kAFS: no volume name specified\n");
return -EINVAL; return -EINVAL;