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jffs2: fix UAF problem

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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@huawei.com>
Reviewed-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Zhe Li 2020-06-19 17:06:35 +08:00 committed by Richard Weinberger
parent a68005a36d
commit 798b7347e4
1 changed files with 5 additions and 1 deletions
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6
fs/jffs2/dir.c
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@ -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);