[PATCH] jffs2: check the validity of dstlen in jffs2_zlib_compress()
From: menglong8 . dong
Date: Thu Jan 28 2021 - 05:56:44 EST
From: Yang Yang <yang.yang29@xxxxxxxxxx>
KASAN reports a BUG when download file in jffs2 filesystem.It is
because when dstlen == 1, cpage_out will write array out of bounds.
Actually, data will not be compressed in jffs2_zlib_compress() if
data's length less than 4.
[ 393.799778] BUG: KASAN: slab-out-of-bounds in jffs2_rtime_compress+0x214/0x2f0 at addr ffff800062e3b281
[ 393.809166] Write of size 1 by task tftp/2918
[ 393.813526] CPU: 3 PID: 2918 Comm: tftp Tainted: G B 4.9.115-rt93-EMBSYS-CGEL-6.1.R6-dirty #1
[ 393.823173] Hardware name: LS1043A RDB Board (DT)
[ 393.827870] Call trace:
[ 393.830322] [<ffff20000808c700>] dump_backtrace+0x0/0x2f0
[ 393.835721] [<ffff20000808ca04>] show_stack+0x14/0x20
[ 393.840774] [<ffff2000086ef700>] dump_stack+0x90/0xb0
[ 393.845829] [<ffff20000827b19c>] kasan_object_err+0x24/0x80
[ 393.851402] [<ffff20000827b404>] kasan_report_error+0x1b4/0x4d8
[ 393.857323] [<ffff20000827bae8>] kasan_report+0x38/0x40
[ 393.862548] [<ffff200008279d44>] __asan_store1+0x4c/0x58
[ 393.867859] [<ffff2000084ce2ec>] jffs2_rtime_compress+0x214/0x2f0
[ 393.873955] [<ffff2000084bb3b0>] jffs2_selected_compress+0x178/0x2a0
[ 393.880308] [<ffff2000084bb530>] jffs2_compress+0x58/0x478
[ 393.885796] [<ffff2000084c5b34>] jffs2_write_inode_range+0x13c/0x450
[ 393.892150] [<ffff2000084be0b8>] jffs2_write_end+0x2a8/0x4a0
[ 393.897811] [<ffff2000081f3008>] generic_perform_write+0x1c0/0x280
[ 393.903990] [<ffff2000081f5074>] __generic_file_write_iter+0x1c4/0x228
[ 393.910517] [<ffff2000081f5210>] generic_file_write_iter+0x138/0x288
[ 393.916870] [<ffff20000829ec1c>] __vfs_write+0x1b4/0x238
[ 393.922181] [<ffff20000829ff00>] vfs_write+0xd0/0x238
[ 393.927232] [<ffff2000082a1ba8>] SyS_write+0xa0/0x110
[ 393.932283] [<ffff20000808429c>] __sys_trace_return+0x0/0x4
[ 393.937851] Object at ffff800062e3b280, in cache kmalloc-64 size: 64
[ 393.944197] Allocated:
[ 393.946552] PID = 2918
[ 393.948913] save_stack_trace_tsk+0x0/0x220
[ 393.953096] save_stack_trace+0x18/0x20
[ 393.956932] kasan_kmalloc+0xd8/0x188
[ 393.960594] __kmalloc+0x144/0x238
[ 393.963994] jffs2_selected_compress+0x48/0x2a0
[ 393.968524] jffs2_compress+0x58/0x478
[ 393.972273] jffs2_write_inode_range+0x13c/0x450
[ 393.976889] jffs2_write_end+0x2a8/0x4a0
[ 393.980810] generic_perform_write+0x1c0/0x280
[ 393.985251] __generic_file_write_iter+0x1c4/0x228
[ 393.990040] generic_file_write_iter+0x138/0x288
[ 393.994655] __vfs_write+0x1b4/0x238
[ 393.998228] vfs_write+0xd0/0x238
[ 394.001543] SyS_write+0xa0/0x110
[ 394.004856] __sys_trace_return+0x0/0x4
[ 394.008684] Freed:
[ 394.010691] PID = 2918
[ 394.013051] save_stack_trace_tsk+0x0/0x220
[ 394.017233] save_stack_trace+0x18/0x20
[ 394.021069] kasan_slab_free+0x88/0x188
[ 394.024902] kfree+0x6c/0x1d8
[ 394.027868] jffs2_sum_write_sumnode+0x2c4/0x880
[ 394.032486] jffs2_do_reserve_space+0x198/0x598
[ 394.037016] jffs2_reserve_space+0x3f8/0x4d8
[ 394.041286] jffs2_write_inode_range+0xf0/0x450
[ 394.045816] jffs2_write_end+0x2a8/0x4a0
[ 394.049737] generic_perform_write+0x1c0/0x280
[ 394.054179] __generic_file_write_iter+0x1c4/0x228
[ 394.058968] generic_file_write_iter+0x138/0x288
[ 394.063583] __vfs_write+0x1b4/0x238
[ 394.067157] vfs_write+0xd0/0x238
[ 394.070470] SyS_write+0xa0/0x110
[ 394.073783] __sys_trace_return+0x0/0x4
[ 394.077612] Memory state around the buggy address:
[ 394.082404] ffff800062e3b180: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
[ 394.089623] ffff800062e3b200: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
[ 394.096842] >ffff800062e3b280: 01 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 394.104056] ^
[ 394.107283] ffff800062e3b300: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
[ 394.114502] ffff800062e3b380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
[ 394.121718] ==================================================================
Signed-off-by: Yang Yang <yang.yang29@xxxxxxxxxx>
---
fs/jffs2/compr_rtime.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/jffs2/compr_rtime.c b/fs/jffs2/compr_rtime.c
index 406d9cc84ba8..79e771ab624f 100644
--- a/fs/jffs2/compr_rtime.c
+++ b/fs/jffs2/compr_rtime.c
@@ -37,6 +37,9 @@ static int jffs2_rtime_compress(unsigned char *data_in,
int outpos = 0;
int pos=0;
+ if (*dstlen <= 3)
+ return -1;
+
memset(positions,0,sizeof(positions));
while (pos < (*sourcelen) && outpos <= (*dstlen)-2) {
--
2.25.1