| Message ID | 20200326053556.20492-4-wqu@suse.com |
|---|---|
| State | Accepted |
| Commit | b941d1cd169e8697ed2e076332cd5526ef9269fb |
| Headers | show |
| Series | fs: btrfs: Fix false LZO decompression error due to missing page boundary check | expand |
On Thu, 26 Mar 2020 13:35:56 +0800 Qu Wenruo <wqu at suse.com> wrote: > For certain btrfs files with compressed file extent, uboot will fail to > load it: > > btrfs_read_extent_reg: disk_bytenr=14229504 disk_len=73728 offset=0 nr_bytes=131 > 072 > decompress_lzo: tot_len=70770 > decompress_lzo: in_len=1389 > decompress_lzo: in_len=2400 > decompress_lzo: in_len=3002 > decompress_lzo: in_len=1379 > decompress_lzo: in_len=88539136 > decompress_lzo: header error, in_len=88539136 clen=65534 tot_len=62580 > > NOTE: except the last line, all other lines are debug output. > > Btrfs lzo compression uses its own format to record compressed size > (segment header, LE32). > > However to make decompression easier, we never put such segment header > across page boundary. > > In above case, the xxd dump of the lzo compressed data looks like this: > > 00001fe0: 4cdc 02fc 0bfd 02c0 dc02 0d13 0100 0001 L............... > 00001ff0: 0000 0008 0300 0000 0000 0011 0000|0000 ................ > 00002000: 4705 0000 0001 cc02 0000 0000 0000 1e01 G............... > > '|' is the "expected" segment header start position. > > But in that page, there are only 2 bytes left, can't contain the 4 bytes > segment header. > > So btrfs compression will skip that 2 bytes, put the segment header in > next page directly. > > Uboot doesn't have such check, and read the header with 2 bytes offset, > result 0x05470000 (88539136), other than the expected result > 0x00000547 (1351), resulting above error. > > Follow the btrfs-progs restore implementation, by introducing tot_in to > record total processed bytes (including headers), and do proper page > boundary skip to fix it. > > Please note that, current code base doesn't parse fs_info thus we can't > grab sector size easily, so it uses PAGE_SIZE, and relying on fs open > time check to exclude unsupported sector size. > > Signed-off-by: Qu Wenruo <wqu at suse.com> > Cc: Marek Behun <marek.behun at nic.cz> > --- > fs/btrfs/compression.c | 20 +++++++++++++++++++- > 1 file changed, 19 insertions(+), 1 deletion(-) > > diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c > index 4ef44ce11485..b1884fc15ee0 100644 > --- a/fs/btrfs/compression.c > +++ b/fs/btrfs/compression.c > @@ -9,6 +9,7 @@ > #include <malloc.h> > #include <linux/lzo.h> > #include <linux/zstd.h> > +#include <linux/compat.h> > #include <u-boot/zlib.h> > #include <asm/unaligned.h> > > @@ -16,7 +17,7 @@ > #define LZO_LEN 4 > static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen) > { > - u32 tot_len, in_len, res; > + u32 tot_len, tot_in, in_len, res; > size_t out_len; > int ret; > > @@ -24,9 +25,11 @@ static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen) > return -1; > > tot_len = le32_to_cpu(get_unaligned((u32 *)cbuf)); > + tot_in = 0; > cbuf += LZO_LEN; > clen -= LZO_LEN; > tot_len -= LZO_LEN; > + tot_in += LZO_LEN; > > if (tot_len == 0 && dlen) > return -1; > @@ -36,6 +39,8 @@ static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen) > res = 0; > > while (tot_len > LZO_LEN) { > + u32 rem_page; > + > in_len = le32_to_cpu(get_unaligned((u32 *)cbuf)); > cbuf += LZO_LEN; > clen -= LZO_LEN; > @@ -44,6 +49,7 @@ static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen) > return -1; > > tot_len -= (LZO_LEN + in_len); > + tot_in += (LZO_LEN + in_len); > > out_len = dlen; > ret = lzo1x_decompress_safe(cbuf, in_len, dbuf, &out_len); > @@ -56,6 +62,18 @@ static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen) > dlen -= out_len; > > res += out_len; > + > + /* > + * If the 4 bytes header does not fit to the rest of the page we > + * have to move to next one, or we read some garbage. > + */ > + rem_page = PAGE_SIZE - (tot_in % PAGE_SIZE); > + if (rem_page < LZO_LEN) { > + cbuf += rem_page; > + tot_in += rem_page; > + clen -= rem_page; > + tot_len -= rem_page; > + } > } > > return res; Reviewed-by: Marek Beh?n <marek.behun at nic.cz>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 4ef44ce11485..b1884fc15ee0 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -9,6 +9,7 @@ #include <malloc.h> #include <linux/lzo.h> #include <linux/zstd.h> +#include <linux/compat.h> #include <u-boot/zlib.h> #include <asm/unaligned.h> @@ -16,7 +17,7 @@ #define LZO_LEN 4 static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen) { - u32 tot_len, in_len, res; + u32 tot_len, tot_in, in_len, res; size_t out_len; int ret; @@ -24,9 +25,11 @@ static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen) return -1; tot_len = le32_to_cpu(get_unaligned((u32 *)cbuf)); + tot_in = 0; cbuf += LZO_LEN; clen -= LZO_LEN; tot_len -= LZO_LEN; + tot_in += LZO_LEN; if (tot_len == 0 && dlen) return -1; @@ -36,6 +39,8 @@ static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen) res = 0; while (tot_len > LZO_LEN) { + u32 rem_page; + in_len = le32_to_cpu(get_unaligned((u32 *)cbuf)); cbuf += LZO_LEN; clen -= LZO_LEN; @@ -44,6 +49,7 @@ static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen) return -1; tot_len -= (LZO_LEN + in_len); + tot_in += (LZO_LEN + in_len); out_len = dlen; ret = lzo1x_decompress_safe(cbuf, in_len, dbuf, &out_len); @@ -56,6 +62,18 @@ static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen) dlen -= out_len; res += out_len; + + /* + * If the 4 bytes header does not fit to the rest of the page we + * have to move to next one, or we read some garbage. + */ + rem_page = PAGE_SIZE - (tot_in % PAGE_SIZE); + if (rem_page < LZO_LEN) { + cbuf += rem_page; + tot_in += rem_page; + clen -= rem_page; + tot_len -= rem_page; + } } return res;
For certain btrfs files with compressed file extent, uboot will fail to load it: btrfs_read_extent_reg: disk_bytenr=14229504 disk_len=73728 offset=0 nr_bytes=131 072 decompress_lzo: tot_len=70770 decompress_lzo: in_len=1389 decompress_lzo: in_len=2400 decompress_lzo: in_len=3002 decompress_lzo: in_len=1379 decompress_lzo: in_len=88539136 decompress_lzo: header error, in_len=88539136 clen=65534 tot_len=62580 NOTE: except the last line, all other lines are debug output. Btrfs lzo compression uses its own format to record compressed size (segment header, LE32). However to make decompression easier, we never put such segment header across page boundary. In above case, the xxd dump of the lzo compressed data looks like this: 00001fe0: 4cdc 02fc 0bfd 02c0 dc02 0d13 0100 0001 L............... 00001ff0: 0000 0008 0300 0000 0000 0011 0000|0000 ................ 00002000: 4705 0000 0001 cc02 0000 0000 0000 1e01 G............... '|' is the "expected" segment header start position. But in that page, there are only 2 bytes left, can't contain the 4 bytes segment header. So btrfs compression will skip that 2 bytes, put the segment header in next page directly. Uboot doesn't have such check, and read the header with 2 bytes offset, result 0x05470000 (88539136), other than the expected result 0x00000547 (1351), resulting above error. Follow the btrfs-progs restore implementation, by introducing tot_in to record total processed bytes (including headers), and do proper page boundary skip to fix it. Please note that, current code base doesn't parse fs_info thus we can't grab sector size easily, so it uses PAGE_SIZE, and relying on fs open time check to exclude unsupported sector size. Signed-off-by: Qu Wenruo <wqu at suse.com> Cc: Marek Behun <marek.behun at nic.cz> --- fs/btrfs/compression.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-)