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[PATCH v2] erofs: fix inconsistent per-file compression format

Gao Xiang posted 1 patch 2 years ago
There is a newer version of this series
fs/erofs/decompressor.c | 2 +-
fs/erofs/zmap.c         | 9 ++++++---
2 files changed, 7 insertions(+), 4 deletions(-)
[PATCH v2] erofs: fix inconsistent per-file compression format
Posted by Gao Xiang 2 years ago 
EROFS can select compression algorithms on a per-file basis, and each
per-file compression algorithm needs to be marked in the on-disk
superblock for initialization.

However, syzkaller can generate inconsistent crafted images that use
an unsupported algorithm for specific inodes; thus, an unexpected
"BUG: kernel NULL pointer dereference" can be raised.

Fix this by checking against `sbi->available_compr_algs` for each
compressed inode.  Incorrect !erofs_sb_has_compr_cfgs preset bitmap
is now fixed together since it was harmless previously.

Reported-by: <bugreport@ubisectech.com>
Fixes: 14373711dd54 ("erofs: add on-disk compression configurations")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
change since v1:
 - fix left-shift overflow (undefined behavior).

 fs/erofs/decompressor.c | 2 +-
 fs/erofs/zmap.c         | 9 ++++++---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index 021be5feb1bc..af98e88908ee 100644
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -398,7 +398,7 @@ int z_erofs_parse_cfgs(struct super_block *sb, struct erofs_super_block *dsb)
 	int size, ret = 0;
 
 	if (!erofs_sb_has_compr_cfgs(sbi)) {
-		sbi->available_compr_algs = Z_EROFS_COMPRESSION_LZ4;
+		sbi->available_compr_algs = 1 << Z_EROFS_COMPRESSION_LZ4;
 		return z_erofs_load_lz4_config(sb, dsb, NULL, 0);
 	}
 
diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index 7b55111fd533..6f10bc8bbb1c 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -578,6 +578,7 @@ static int z_erofs_fill_inode_lazy(struct inode *inode)
 {
 	struct erofs_inode *const vi = EROFS_I(inode);
 	struct super_block *const sb = inode->i_sb;
+	struct erofs_sb_info *sbi = EROFS_SB(sb);
 	int err, headnr;
 	erofs_off_t pos;
 	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
@@ -624,10 +625,12 @@ static int z_erofs_fill_inode_lazy(struct inode *inode)
 
 	headnr = 0;
 	if (vi->z_algorithmtype[0] >= Z_EROFS_COMPRESSION_MAX ||
-	    vi->z_algorithmtype[++headnr] >= Z_EROFS_COMPRESSION_MAX) {
-		erofs_err(sb, "unknown HEAD%u format %u for nid %llu, please upgrade kernel",
+	    !(sbi->available_compr_algs & (1 << vi->z_algorithmtype[0])) ||
+	    vi->z_algorithmtype[++headnr] >= Z_EROFS_COMPRESSION_MAX ||
+	    !(sbi->available_compr_algs & (1 << vi->z_algorithmtype[headnr]))) {
+		erofs_err(sb, "inconsistent HEAD%u algorithm format %u for nid %llu",
 			  headnr + 1, vi->z_algorithmtype[headnr], vi->nid);
-		err = -EOPNOTSUPP;
+		err = -EFSCORRUPTED;
 		goto out_put_metabuf;
 	}
 
-- 
2.39.3
Re: [PATCH v2] erofs: fix inconsistent per-file compression format
Posted by Yue Hu 1 year, 12 months ago 
On Wed, 27 Dec 2023 13:06:33 +0800
Gao Xiang <hsiangkao@linux.alibaba.com> wrote:

> EROFS can select compression algorithms on a per-file basis, and each
> per-file compression algorithm needs to be marked in the on-disk
> superblock for initialization.
> 
> However, syzkaller can generate inconsistent crafted images that use
> an unsupported algorithm for specific inodes; thus, an unexpected
> "BUG: kernel NULL pointer dereference" can be raised.
> 
> Fix this by checking against `sbi->available_compr_algs` for each
> compressed inode.  Incorrect !erofs_sb_has_compr_cfgs preset bitmap
> is now fixed together since it was harmless previously.
> 
> Reported-by: <bugreport@ubisectech.com>
> Fixes: 14373711dd54 ("erofs: add on-disk compression configurations")
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Reviewed-by: Yue Hu <huyue2@coolpad.com>
[PATCH v3] erofs: fix inconsistent per-file compression format
Posted by Gao Xiang 1 year, 11 months ago 
EROFS can select compression algorithms on a per-file basis, and each
per-file compression algorithm needs to be marked in the on-disk
superblock for initialization.

However, syzkaller can generate inconsistent crafted images that use
an unsupported algorithmtype for specific inodes, e.g. use MicroLZMA
algorithmtype even it's not set in `sbi->available_compr_algs`.  This
can lead to an unexpected "BUG: kernel NULL pointer dereference" if
the corresponding decompressor isn't built-in.

Fix this by checking against `sbi->available_compr_algs` for each
m_algorithmformat request.  Incorrect !erofs_sb_has_compr_cfgs preset
bitmap is now fixed together since it was harmless previously.

Reported-by: <bugreport@ubisectech.com>
Fixes: 8f89926290c4 ("erofs: get compression algorithms directly on mapping")
Fixes: 622ceaddb764 ("erofs: lzma compression support")
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
changes since v2:
 - Should check in z_erofs_do_map_blocks() runtimely since another
   algorithmtype[0/1] could leave as unused (0) but it can be
   problematic if LZ4 is not set in `sbi->available_compr_algs`.

 fs/erofs/decompressor.c |  2 +-
 fs/erofs/zmap.c         | 23 +++++++++++++----------
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index 1d65b9f60a39..072ef6a66823 100644
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -408,7 +408,7 @@ int z_erofs_parse_cfgs(struct super_block *sb, struct erofs_super_block *dsb)
 	int size, ret = 0;
 
 	if (!erofs_sb_has_compr_cfgs(sbi)) {
-		sbi->available_compr_algs = Z_EROFS_COMPRESSION_LZ4;
+		sbi->available_compr_algs = 1 << Z_EROFS_COMPRESSION_LZ4;
 		return z_erofs_load_lz4_config(sb, dsb, NULL, 0);
 	}
 
diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index 9753875e41cb..7e1116804008 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -454,7 +454,7 @@ static int z_erofs_do_map_blocks(struct inode *inode,
 		.map = map,
 	};
 	int err = 0;
-	unsigned int lclusterbits, endoff;
+	unsigned int lclusterbits, endoff, afmt;
 	unsigned long initial_lcn;
 	unsigned long long ofs, end;
 
@@ -543,17 +543,20 @@ static int z_erofs_do_map_blocks(struct inode *inode,
 			err = -EFSCORRUPTED;
 			goto unmap_out;
 		}
-		if (vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER)
-			map->m_algorithmformat =
-				Z_EROFS_COMPRESSION_INTERLACED;
-		else
-			map->m_algorithmformat =
-				Z_EROFS_COMPRESSION_SHIFTED;
-	} else if (m.headtype == Z_EROFS_LCLUSTER_TYPE_HEAD2) {
-		map->m_algorithmformat = vi->z_algorithmtype[1];
+		afmt = vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER ?
+			Z_EROFS_COMPRESSION_INTERLACED :
+			Z_EROFS_COMPRESSION_SHIFTED;
 	} else {
-		map->m_algorithmformat = vi->z_algorithmtype[0];
+		afmt = m.headtype == Z_EROFS_LCLUSTER_TYPE_HEAD2 ?
+			vi->z_algorithmtype[1] : vi->z_algorithmtype[0];
+		if (!(EROFS_I_SB(inode)->available_compr_algs & (1 << afmt))) {
+			erofs_err(inode->i_sb, "inconsistent algorithmtype %u for nid %llu",
+				  afmt, vi->nid);
+			err = -EFSCORRUPTED;
+			goto unmap_out;
+		}
 	}
+	map->m_algorithmformat = afmt;
 
 	if ((flags & EROFS_GET_BLOCKS_FIEMAP) ||
 	    ((flags & EROFS_GET_BLOCKS_READMORE) &&
-- 
2.39.3
Re: [PATCH v3] erofs: fix inconsistent per-file compression format
Posted by Yue Hu 1 year, 11 months ago 
On Sat, 13 Jan 2024 23:06:02 +0800
Gao Xiang <hsiangkao@linux.alibaba.com> wrote:

> EROFS can select compression algorithms on a per-file basis, and each
> per-file compression algorithm needs to be marked in the on-disk
> superblock for initialization.
> 
> However, syzkaller can generate inconsistent crafted images that use
> an unsupported algorithmtype for specific inodes, e.g. use MicroLZMA
> algorithmtype even it's not set in `sbi->available_compr_algs`.  This
> can lead to an unexpected "BUG: kernel NULL pointer dereference" if
> the corresponding decompressor isn't built-in.
> 
> Fix this by checking against `sbi->available_compr_algs` for each
> m_algorithmformat request.  Incorrect !erofs_sb_has_compr_cfgs preset
> bitmap is now fixed together since it was harmless previously.
> 
> Reported-by: <bugreport@ubisectech.com>
> Fixes: 8f89926290c4 ("erofs: get compression algorithms directly on mapping")
> Fixes: 622ceaddb764 ("erofs: lzma compression support")
> Reviewed-by: Yue Hu <huyue2@coolpad.com>
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

LGTM.

Reviewed-by: Yue Hu <huyue2@coolpad.com>

Patchew 2.1-devel-b67e4c2

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