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    Subject[PATCH 5.4 025/453] afs: Fix memory leak when mounting with multiple source parameters
    Date
    From: David Howells <dhowells@redhat.com>

    [ Upstream commit 4cb682964706deffb4861f0a91329ab3a705039f ]

    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: 13fcc6837049 ("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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/afs/super.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/fs/afs/super.c b/fs/afs/super.c
    index 7f8a9b3137bff..eb04dcc543289 100644
    --- a/fs/afs/super.c
    +++ b/fs/afs/super.c
    @@ -236,6 +236,9 @@ static int afs_parse_source(struct fs_context *fc, struct fs_parameter *param)

    _enter(",%s", name);

    + if (fc->source)
    + return invalf(fc, "kAFS: Multiple sources not supported");
    +
    if (!name) {
    printk(KERN_ERR "kAFS: no volume name specified\n");
    return -EINVAL;
    --
    2.27.0


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