btrfs: lzo: Harden decompression callers to avoid kernel memory corruption.

James Harvey reported that some corrupted compressed extent data can lead to various kernel memory corruption.

Such corrupted extent data belongs to inode with NODATASUM flags, thus data csum won't help us detecting such bug.

If lucky enough, kasan could catch it like:
==================================================================

BUG: KASAN: slab-out-of-bounds in lzo_decompress_bio+0x384/0x7a0 [btrfs]
Write of size 4096 at addr ffff8800606cb0f8 by task kworker/u16:0/2338

CPU: 3 PID: 2338 Comm: kworker/u16:0 Tainted: G           O      4.17.0-rc5-custom+ #50
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Workqueue: btrfs-endio btrfs_endio_helper [btrfs]
Call Trace:
 dump_stack+0xc2/0x16b
 print_address_description+0x6a/0x270
 kasan_report+0x260/0x380
 memcpy+0x34/0x50
 lzo_decompress_bio+0x384/0x7a0 [btrfs]
 end_compressed_bio_read+0x99f/0x10b0 [btrfs]
 bio_endio+0x32e/0x640
 normal_work_helper+0x15a/0xea0 [btrfs]
 process_one_work+0x7e3/0x1470
 worker_thread+0x1b0/0x1170
 kthread+0x2db/0x390
 ret_from_fork+0x22/0x40

...
==================================================================

The offending compressed data has the following info:

Header: length 32768 (Looks completely valid)
Segment 0 Header: length 3472882419 (Obvious out of bounds)

Then when handling segment 0, since it's over the current page, we need the compressed data to workspace, then such large size would trigger out-of-bounds memory access, screwing up the whole kernel.

Fix it by adding extra checks on header and segment headers to ensure we won't access out-of-bounds, and even checks the decompressed data won't be out-of-bounds.

Reported-by James Harvey <[email protected]>

Signed-off-by Qu Wenruo <[email protected]>

---
 fs/btrfs/lzo.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

fs/btrfs/lzo.c +6 -0

index ec5db393c758..4f4de460b08d 100644
@@ -293,6 +293,7 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 	unsigned long working_bytes;
 	size_t in_len;
 	size_t out_len;
+	size_t max_segment_len = lzo1x_worst_compress(PAGE_SIZE);
 	unsigned long in_offset;
 	unsigned long in_page_bytes_left;
 	unsigned long tot_in;

@@ -306,6 +307,18 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 
 	data_in = kmap(pages_in[0]);
 	tot_len = read_compress_length(data_in);
+	/*
+	 * Compressed data header check.
+	 *
+	 * The real compressed size can't exceed extent length, and all pages
+	 * should be used (a full pending page is not possible).

fs/btrfs/lzo.c +21 -1

@@ -320,6 +333,17 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 		in_offset += LZO_LEN;
 		tot_in += LZO_LEN;
 
+		/*
+		 * Segment header check.
+		 *
+		 * The segment length must not exceed max lzo compression
+		 * size, nor the total compressed size
+		 */
+		if (in_len > max_segment_len || tot_in + in_len > tot_len) {
+			ret = -EUCLEAN;
+			goto done;
+		}
+
 		tot_in += in_len;
 		working_bytes = in_len;
 		may_late_unmap = need_unmap = false;

@@ -370,7 +394,7 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 			}
 		}
 
-		out_len = lzo1x_worst_compress(PAGE_SIZE);
+		out_len = max_segment_len;
 		ret = lzo1x_decompress_safe(buf, in_len, workspace->buf,
 					    &out_len);
 		if (need_unmap)

@@ -380,6 +404,15 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 			ret = -EIO;
 			break;
 		}
+		/*
+		 * Decompressed data length check.
+		 * The uncompressed data should not exceed uncompressed extent
+		 * size.
+		 */
+		if (tot_out + out_len > cb->len) {
+			ret = -EUCLEAN;
+			break;
+		}
 
 		buf_start = tot_out;
 		tot_out += out_len;

Quoted 78 lines · Qu Wenruo

James Harvey reported that some corrupted compressed extent data can lead to various kernel memory corruption.

Such corrupted extent data belongs to inode with NODATASUM flags, thus data csum won't help us detecting such bug.

If lucky enough, kasan could catch it like:
==================================================================

BUG: KASAN: slab-out-of-bounds in lzo_decompress_bio+0x384/0x7a0 [btrfs]
Write of size 4096 at addr ffff8800606cb0f8 by task kworker/u16:0/2338

CPU: 3 PID: 2338 Comm: kworker/u16:0 Tainted: G           O      4.17.0-rc5-custom+ #50
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Workqueue: btrfs-endio btrfs_endio_helper [btrfs]
Call Trace:
 dump_stack+0xc2/0x16b
 print_address_description+0x6a/0x270
 kasan_report+0x260/0x380
 memcpy+0x34/0x50
 lzo_decompress_bio+0x384/0x7a0 [btrfs]
 end_compressed_bio_read+0x99f/0x10b0 [btrfs]
 bio_endio+0x32e/0x640
 normal_work_helper+0x15a/0xea0 [btrfs]
 process_one_work+0x7e3/0x1470
 worker_thread+0x1b0/0x1170
 kthread+0x2db/0x390
 ret_from_fork+0x22/0x40

...
==================================================================

The offending compressed data has the following info:

Header: length 32768 (Looks completely valid)
Segment 0 Header: length 3472882419 (Obvious out of bounds)

Then when handling segment 0, since it's over the current page, we need the compressed data to workspace, then such large size would trigger out-of-bounds memory access, screwing up the whole kernel.

Fix it by adding extra checks on header and segment headers to ensure we won't access out-of-bounds, and even checks the decompressed data won't be out-of-bounds.

Reported-by James Harvey <[email protected]>

Signed-off-by Qu Wenruo <[email protected]>

---
 fs/btrfs/lzo.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

fs/btrfs/lzo.c +13 -0

index ec5db393c758..4f4de460b08d 100644
@@ -293,6 +293,7 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 	unsigned long working_bytes;
 	size_t in_len;
 	size_t out_len;
+	size_t max_segment_len = lzo1x_worst_compress(PAGE_SIZE);
 	unsigned long in_offset;
 	unsigned long in_page_bytes_left;
 	unsigned long tot_in;

@@ -306,6 +307,18 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 
 	data_in = kmap(pages_in[0]);
 	tot_len = read_compress_length(data_in);
+	/*
+	 * Compressed data header check.
+	 *
+	 * The real compressed size can't exceed extent length, and all pages
+	 * should be used (a full pending page is not possible).
+	 * If this happens it means the compressed extent is corrupted.
+	 */
+	if (tot_len > min_t(size_t, BTRFS_MAX_COMPRESSED, srclen) ||
+	    tot_len < srclen - PAGE_SIZE) {
+		ret = -EUCLEAN;
+		goto done;
+	}
 

fs/btrfs/lzo.c static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb) · line 324

Quoted 2 lines

fs/btrfs/lzo.c +0 -0

 	tot_in = LZO_LEN;
 	in_offset = LZO_LEN;

Just 1 line below here is:

        tot_len = min_t(size_t, srclen, tot_len);

but this is not needed because always tot_len <= srclen, considered above if, right?

Quoted 35 lines

fs/btrfs/lzo.c +14 -1

@@ -320,6 +333,17 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 		in_offset += LZO_LEN;
 		tot_in += LZO_LEN;
 
+		/*
+		 * Segment header check.
+		 *
+		 * The segment length must not exceed max lzo compression
+		 * size, nor the total compressed size
+		 */
+		if (in_len > max_segment_len || tot_in + in_len > tot_len) {
+			ret = -EUCLEAN;
+			goto done;
+		}
+
 		tot_in += in_len;
 		working_bytes = in_len;
 		may_late_unmap = need_unmap = false;

@@ -370,7 +394,7 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 			}
 		}
 
-		out_len = lzo1x_worst_compress(PAGE_SIZE);
+		out_len = max_segment_len;
 		ret = lzo1x_decompress_safe(buf, in_len, workspace->buf,
 					    &out_len);
 		if (need_unmap)

@@ -380,6 +404,15 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 			ret = -EIO;
 			break;
 		}
+		/*
+		 * Decompressed data length check.

fs/btrfs/lzo.c static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb) · line 418

Quoted 10 lines

fs/btrfs/lzo.c +7 -0

+		 * The uncompressed data should not exceed uncompressed extent
+		 * size.
+		 */
+		if (tot_out + out_len > cb->len) {
+			ret = -EUCLEAN;
+			break;
+		}
 
 		buf_start = tot_out;
 		tot_out += out_len;

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James Harvey reported that some corrupted compressed extent data can lead to various kernel memory corruption.

Such corrupted extent data belongs to inode with NODATASUM flags, thus data csum won't help us detecting such bug.

If lucky enough, kasan could catch it like:
==================================================================

BUG: KASAN: slab-out-of-bounds in lzo_decompress_bio+0x384/0x7a0 [btrfs]
Write of size 4096 at addr ffff8800606cb0f8 by task kworker/u16:0/2338

CPU: 3 PID: 2338 Comm: kworker/u16:0 Tainted: G           O      4.17.0-rc5-custom+ #50
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Workqueue: btrfs-endio btrfs_endio_helper [btrfs]
Call Trace:
 dump_stack+0xc2/0x16b
 print_address_description+0x6a/0x270
 kasan_report+0x260/0x380
 memcpy+0x34/0x50
 lzo_decompress_bio+0x384/0x7a0 [btrfs]
 end_compressed_bio_read+0x99f/0x10b0 [btrfs]
 bio_endio+0x32e/0x640
 normal_work_helper+0x15a/0xea0 [btrfs]
 process_one_work+0x7e3/0x1470
 worker_thread+0x1b0/0x1170
 kthread+0x2db/0x390
 ret_from_fork+0x22/0x40

...
==================================================================

The offending compressed data has the following info:

Header: length 32768 (Looks completely valid)
Segment 0 Header: length 3472882419 (Obvious out of bounds)

Then when handling segment 0, since it's over the current page, we need the compressed data to workspace, then such large size would trigger out-of-bounds memory access, screwing up the whole kernel.

Fix it by adding extra checks on header and segment headers to ensure we won't access out-of-bounds, and even checks the decompressed data won't be out-of-bounds.

Reported-by James Harvey <[email protected]>

Signed-off-by Qu Wenruo <[email protected]>

---
 fs/btrfs/lzo.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

fs/btrfs/lzo.c +25 -1

index ec5db393c758..4f4de460b08d 100644
@@ -293,6 +293,7 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 	unsigned long working_bytes;
 	size_t in_len;
 	size_t out_len;
+	size_t max_segment_len = lzo1x_worst_compress(PAGE_SIZE);
 	unsigned long in_offset;
 	unsigned long in_page_bytes_left;
 	unsigned long tot_in;

@@ -306,6 +307,18 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 
 	data_in = kmap(pages_in[0]);
 	tot_len = read_compress_length(data_in);
+	/*
+	 * Compressed data header check.
+	 *
+	 * The real compressed size can't exceed extent length, and all pages
+	 * should be used (a full pending page is not possible).
+	 * If this happens it means the compressed extent is corrupted.
+	 */
+	if (tot_len > min_t(size_t, BTRFS_MAX_COMPRESSED, srclen) ||
+	    tot_len < srclen - PAGE_SIZE) {
+		ret = -EUCLEAN;
+		goto done;
+	}
 
 	tot_in = LZO_LEN;
 	in_offset = LZO_LEN;

@@ -320,6 +333,17 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 		in_offset += LZO_LEN;
 		tot_in += LZO_LEN;
 
+		/*
+		 * Segment header check.
+		 *
+		 * The segment length must not exceed max lzo compression
+		 * size, nor the total compressed size
+		 */
+		if (in_len > max_segment_len || tot_in + in_len > tot_len) {
+			ret = -EUCLEAN;
+			goto done;
+		}
+
 		tot_in += in_len;
 		working_bytes = in_len;
 		may_late_unmap = need_unmap = false;

@@ -370,7 +394,7 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 			}
 		}
 
-		out_len = lzo1x_worst_compress(PAGE_SIZE);
+		out_len = max_segment_len;
 		ret = lzo1x_decompress_safe(buf, in_len, workspace->buf,
 					    &out_len);
 		if (need_unmap)

@@ -380,6 +404,15 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 			ret = -EIO;
 			break;
 		}
 

fs/btrfs/lzo.c +0 -0

 		buf_start = tot_out;

tot_out += out_len;

Quoted 112 lines · Qu Wenruo

James Harvey reported that some corrupted compressed extent data can lead to various kernel memory corruption.

Such corrupted extent data belongs to inode with NODATASUM flags, thus data csum won't help us detecting such bug.

If lucky enough, kasan could catch it like:
==================================================================

BUG: KASAN: slab-out-of-bounds in lzo_decompress_bio+0x384/0x7a0 [btrfs]
Write of size 4096 at addr ffff8800606cb0f8 by task kworker/u16:0/2338

CPU: 3 PID: 2338 Comm: kworker/u16:0 Tainted: G           O      4.17.0-rc5-custom+ #50
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Workqueue: btrfs-endio btrfs_endio_helper [btrfs]
Call Trace:
 dump_stack+0xc2/0x16b
 print_address_description+0x6a/0x270
 kasan_report+0x260/0x380
 memcpy+0x34/0x50
 lzo_decompress_bio+0x384/0x7a0 [btrfs]
 end_compressed_bio_read+0x99f/0x10b0 [btrfs]
 bio_endio+0x32e/0x640
 normal_work_helper+0x15a/0xea0 [btrfs]
 process_one_work+0x7e3/0x1470
 worker_thread+0x1b0/0x1170
 kthread+0x2db/0x390
 ret_from_fork+0x22/0x40

...
==================================================================

The offending compressed data has the following info:

Header: length 32768 (Looks completely valid)
Segment 0 Header: length 3472882419 (Obvious out of bounds)

Then when handling segment 0, since it's over the current page, we need the compressed data to workspace, then such large size would trigger out-of-bounds memory access, screwing up the whole kernel.

Fix it by adding extra checks on header and segment headers to ensure we won't access out-of-bounds, and even checks the decompressed data won't be out-of-bounds.

Reported-by James Harvey <[email protected]>

Signed-off-by Qu Wenruo <[email protected]>

---
 fs/btrfs/lzo.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

fs/btrfs/lzo.c +25 -1

index ec5db393c758..4f4de460b08d 100644
@@ -293,6 +293,7 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 	unsigned long working_bytes;
 	size_t in_len;
 	size_t out_len;
+	size_t max_segment_len = lzo1x_worst_compress(PAGE_SIZE);
 	unsigned long in_offset;
 	unsigned long in_page_bytes_left;
 	unsigned long tot_in;

@@ -306,6 +307,18 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 
 	data_in = kmap(pages_in[0]);
 	tot_len = read_compress_length(data_in);
+	/*
+	 * Compressed data header check.
+	 *
+	 * The real compressed size can't exceed extent length, and all pages
+	 * should be used (a full pending page is not possible).
+	 * If this happens it means the compressed extent is corrupted.
+	 */
+	if (tot_len > min_t(size_t, BTRFS_MAX_COMPRESSED, srclen) ||
+	    tot_len < srclen - PAGE_SIZE) {
+		ret = -EUCLEAN;
+		goto done;
+	}
 
 	tot_in = LZO_LEN;
 	in_offset = LZO_LEN;

@@ -320,6 +333,17 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 		in_offset += LZO_LEN;
 		tot_in += LZO_LEN;
 
+		/*
+		 * Segment header check.
+		 *
+		 * The segment length must not exceed max lzo compression
+		 * size, nor the total compressed size
+		 */
+		if (in_len > max_segment_len || tot_in + in_len > tot_len) {
+			ret = -EUCLEAN;
+			goto done;
+		}
+
 		tot_in += in_len;
 		working_bytes = in_len;
 		may_late_unmap = need_unmap = false;

@@ -370,7 +394,7 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 			}
 		}
 
-		out_len = lzo1x_worst_compress(PAGE_SIZE);
+		out_len = max_segment_len;
 		ret = lzo1x_decompress_safe(buf, in_len, workspace->buf,
 					    &out_len);
 		if (need_unmap)

@@ -380,6 +404,15 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 			ret = -EIO;
 			break;
 		}
 

fs/btrfs/lzo.c static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb) · line 417

Quoted 10 lines

fs/btrfs/lzo.c +9 -0

 
+		/*
+		 * Decompressed data length check.
+		 * The uncompressed data should not exceed uncompressed extent
+		 * size.
+		 */
+		if (tot_out + out_len > cb->len) {
+			ret = -EUCLEAN;
+			break;
+		}

I observed this part causes some failure of lzo related xfstests (038, 056, 103, 138).

It seems that when pages to be read start from middle of (shared) extents, they needs to be decompressed from the beginning, and therefore (tot_out + out_len) can exceeds cb->len.

Simplified version of btrfs/103 can be used to observe this:
=====
CLONER=/path/to/xfstest/src/cloner
mkfs.btrfs -fq $DEV
mount -o compress=lzo $DEV /mnt

 # make 1 extent (skip 1st 4k)
 xfs_io -f \
   -c "pwrite -S 0xaa 4096 4096" \
   -c "pwrite -S 0xbb 8192 4096" \
   /mnt/bar > /dev/null 2>&1
 # clone second half of above extent to beginning of the file
 $CLONER -s 8192 -d 0 -l 4096 /mnt/foo /mnt/foo

umount /mnt
mount $DEV /mnt

# Input/Output error happens
od -t x1 /mnt/foo
=====

btrfs_decompress_buf2page() skips copy if decompressed region is not
a part of pages to be read. Also, it will copy at most bio->bi_iter.bi_size as code says:

(compression.c)
1183 bio_advance(bio, bytes);
1184 if (!bio->bi_iter.bi_size)
1185 return 0;

cb->len is set to bio->bi_iter.bi_size in btrfs_submit_compressed_read().

So, I think it is ok to remove above "if (tot_out + out_len > cb->len)". Or, should other conditions be checked?

Thanks,
Tomohiro Misono

Quoted 4 lines

fs/btrfs/lzo.c +0 -0

 		buf_start = tot_out;

tot_out += out_len;

James Harvey reported that some corrupted compressed extent data can lead to various kernel memory corruption.

Such corrupted extent data belongs to inode with NODATASUM flags, thus data csum won't help us detecting such bug.

If lucky enough, kasan could catch it like:
==================================================================

BUG: KASAN: slab-out-of-bounds in lzo_decompress_bio+0x384/0x7a0 [btrfs]
Write of size 4096 at addr ffff8800606cb0f8 by task kworker/u16:0/2338

CPU: 3 PID: 2338 Comm: kworker/u16:0 Tainted: G           O      4.17.0-rc5-custom+ #50
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Workqueue: btrfs-endio btrfs_endio_helper [btrfs]
Call Trace:
 dump_stack+0xc2/0x16b
 print_address_description+0x6a/0x270
 kasan_report+0x260/0x380
 memcpy+0x34/0x50
 lzo_decompress_bio+0x384/0x7a0 [btrfs]
 end_compressed_bio_read+0x99f/0x10b0 [btrfs]
 bio_endio+0x32e/0x640
 normal_work_helper+0x15a/0xea0 [btrfs]
 process_one_work+0x7e3/0x1470
 worker_thread+0x1b0/0x1170
 kthread+0x2db/0x390
 ret_from_fork+0x22/0x40

...
==================================================================

The offending compressed data has the following info:

Header: length 32768 (Looks completely valid)
Segment 0 Header: length 3472882419 (Obvious out of bounds)

Then when handling segment 0, since it's over the current page, we need the compressed data to workspace, then such large size would trigger out-of-bounds memory access, screwing up the whole kernel.

Fix it by adding extra checks on header and segment headers to ensure we won't access out-of-bounds, and even checks the decompressed data won't be out-of-bounds.

Reported-by James Harvey <[email protected]>

Signed-off-by Qu Wenruo <[email protected]>

---
changelog:
v3->v4:
Remove the incorrect decompression output length check. For compressed extent with offset, its cb->len is no longer the full uncompressed extent size.
For decompressed size check, it's alraedy done in btrfs_decompress_buf2page(), thus we don't need this incorrect check here. Thanks Misono for pointing this out.

---
 fs/btrfs/lzo.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

fs/btrfs/lzo.c +25 -2

index ec5db393c758..995a96b51b38 100644
@@ -293,6 +293,7 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 	unsigned long working_bytes;
 	size_t in_len;
 	size_t out_len;
+	size_t max_segment_len = lzo1x_worst_compress(PAGE_SIZE);
 	unsigned long in_offset;
 	unsigned long in_page_bytes_left;
 	unsigned long tot_in;

@@ -306,10 +307,21 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 
 	data_in = kmap(pages_in[0]);
 	tot_len = read_compress_length(data_in);
+	/*
+	 * Compressed data header check.
+	 *
+	 * The real compressed size can't exceed extent length, and all pages
+	 * should be used (a full pending page is not possible).
+	 * If this happens it means the compressed extent is corrupted.
+	 */
+	if (tot_len > min_t(size_t, BTRFS_MAX_COMPRESSED, srclen) ||
+	    tot_len < srclen - PAGE_SIZE) {
+		ret = -EUCLEAN;
+		goto done;
+	}
 
 	tot_in = LZO_LEN;
 	in_offset = LZO_LEN;
-	tot_len = min_t(size_t, srclen, tot_len);
 	in_page_bytes_left = PAGE_SIZE - LZO_LEN;
 
 	tot_out = 0;

@@ -320,6 +332,17 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 		in_offset += LZO_LEN;
 		tot_in += LZO_LEN;
 
+		/*
+		 * Segment header check.
+		 *
+		 * The segment length must not exceed max lzo compression
+		 * size, nor the total compressed size
+		 */
+		if (in_len > max_segment_len || tot_in + in_len > tot_len) {
+			ret = -EUCLEAN;
+			goto done;
+		}
+
 		tot_in += in_len;
 		working_bytes = in_len;
 		may_late_unmap = need_unmap = false;

@@ -370,7 +393,7 @@ static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 			}
 		}
 
-		out_len = lzo1x_worst_compress(PAGE_SIZE);
+		out_len = max_segment_len;
 		ret = lzo1x_decompress_safe(buf, in_len, workspace->buf,
 					    &out_len);
 		if (need_unmap)

Reported-by James Harvey <[email protected]>

Signed-off-by Qu Wenruo <[email protected]>

---
changelog:
v3->v4:

James Harvey reported pretty strange kernel misbehavior where after reading certain btrfs compressed data, kernel crash with unrelated calltrace.
(https://bugzilla.kernel.org/show_bug.cgi?id=199707 and
https://www.spinics.net/lists/linux-btrfs/msg77971.html)

Thanks for his comprehensive debug help, we located the problem to:

v3:
Fix comment error for inlined lzo compressed extent. (Still has header), thanks David for pointing this out.
Add example ascii graph as an example.
Enhance inlined extent check, as header length must match with segment header length + LZO_LEN * 2.

Qu Wenruo (4):
btrfs: compression: Add linux/sizes.h for compression.h
btrfs: lzo: Add comment about the how btrfs records its lzo compressed
data
btrfs: lzo: Add header length check to avoid slab out of bounds access
btrfs: lzo: Harden inline lzo compressed extent decompression