Re: [PATCH] jffs2: fix UAF problem
From: Joakim Tjernlund
Date: Wed Jun 24 2020 - 14:59:59 EST
Nice find, I just came across a deadlock wrt GC and rmdir,
hopefully this is he fix.
This needs to go to stable too, sooner rather than later.
Jocke
On Fri, 2020-06-19 at 17:06 +0800, Zhe Li wrote:
>
> The log of UAF problem is listed below.
> BUG: KASAN: use-after-free in jffs2_rmdir+0xa4/0x1cc [jffs2] at addr c1f165fc
> Read of size 4 by task rm/8283
> =============================================================================
> BUG kmalloc-32 (Tainted: P B O ): kasan: bad access detected
> -----------------------------------------------------------------------------
>
> INFO: Allocated in 0xbbbbbbbb age=3054364 cpu=0 pid=0
> 0xb0bba6ef
> jffs2_write_dirent+0x11c/0x9c8 [jffs2]
> __slab_alloc.isra.21.constprop.25+0x2c/0x44
> __kmalloc+0x1dc/0x370
> jffs2_write_dirent+0x11c/0x9c8 [jffs2]
> jffs2_do_unlink+0x328/0x5fc [jffs2]
> jffs2_rmdir+0x110/0x1cc [jffs2]
> vfs_rmdir+0x180/0x268
> do_rmdir+0x2cc/0x300
> ret_from_syscall+0x0/0x3c
> INFO: Freed in 0x205b age=3054364 cpu=0 pid=0
> 0x2e9173
> jffs2_add_fd_to_list+0x138/0x1dc [jffs2]
> jffs2_add_fd_to_list+0x138/0x1dc [jffs2]
> jffs2_garbage_collect_dirent.isra.3+0x21c/0x288 [jffs2]
> jffs2_garbage_collect_live+0x16bc/0x1800 [jffs2]
> jffs2_garbage_collect_pass+0x678/0x11d4 [jffs2]
> jffs2_garbage_collect_thread+0x1e8/0x3b0 [jffs2]
> kthread+0x1a8/0x1b0
> ret_from_kernel_thread+0x5c/0x64
> Call Trace:
> [c17ddd20] [c02452d4] kasan_report.part.0+0x298/0x72c (unreliable)
> [c17ddda0] [d2509680] jffs2_rmdir+0xa4/0x1cc [jffs2]
> [c17dddd0] [c026da04] vfs_rmdir+0x180/0x268
> [c17dde00] [c026f4e4] do_rmdir+0x2cc/0x300
> [c17ddf40] [c001a658] ret_from_syscall+0x0/0x3c
>
> The root cause is that we don't get "jffs2_inode_info.sem" before
> we scan list "jffs2_inode_info.dents" in function jffs2_rmdir.
> This patch add codes to get "jffs2_inode_info.sem" before we scan
> "jffs2_inode_info.dents" to slove the UAF problem.
>
> Signed-off-by: Zhe Li <lizhe67@xxxxxxxxxx>
> ---
> fs/jffs2/dir.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/fs/jffs2/dir.c b/fs/jffs2/dir.c
> index f20cff1..7764937 100644
> --- a/fs/jffs2/dir.c
> +++ b/fs/jffs2/dir.c
> @@ -590,10 +590,14 @@ static int jffs2_rmdir (struct inode *dir_i, struct dentry *dentry)
> int ret;
> uint32_t now = JFFS2_NOW();
>
> + mutex_lock(&f->sem);
> for (fd = f->dents ; fd; fd = fd->next) {
> - if (fd->ino)
> + if (fd->ino) {
> + mutex_unlock(&f->sem);
> return -ENOTEMPTY;
> + }
> }
> + mutex_unlock(&f->sem);
>
> ret = jffs2_do_unlink(c, dir_f, dentry->d_name.name,
> dentry->d_name.len, f, now);
> --
> 2.7.4
>
>
>
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