On Thu, 26 Mar 2020 13:35:56 +0800 Qu Wenruo <w...@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 <w...@suse.com> > Cc: Marek Behun <marek.be...@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 BehĂșn <marek.be...@nic.cz>