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Date: Thu, 25 Nov 2010 21:22:23 +0200
From: Lasse Collin <lasse.collin@...aani.org>
To: linux-kernel@...r.kernel.org
Cc: "H. Peter Anvin" <hpa@...or.com>, Alain Knaff <alain@...ff.lu>,
Albin Tonnerre <albin.tonnerre@...e-electrons.com>,
Phillip Lougher <phillip@...gher.demon.co.uk>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCHv2] Decompressors: Check for write errors in decompress_unlzma.c
From: Lasse Collin <lasse.collin@...aani.org>
The return value of wr->flush() is not checked in write_byte().
This means that the decompressor won't stop even if the caller
doesn't want more data. This can happen e.g. with corrupt
LZMA-compressed initramfs. Returning the error quickly allows
the user to see the error message quicker.
There is a similar missing check for wr.flush() near the end
of unlzma(). It was also possible that with bad luck wr.flush()
would get called with an empty buffer at the end of successful
decompression.
Signed-off-by: Lasse Collin <lasse.collin@...aani.org>
---
Compared to the first version, this ensures that wr.flush()
is not called with an empty buffer. Thanks to Phillip Lougher
for pointing out that flushing empty buffers should be avoided.
This is a replacement for the patch
decompressors-check-for-write-errors-in-decompress_unlzmac.patch
in the -mm tree.
--- linux-2.6.37-rc3/lib/decompress_unlzma.c.orig 2010-11-23 11:10:07.000000000 +0200
+++ linux-2.6.37-rc3/lib/decompress_unlzma.c 2010-11-25 20:51:11.000000000 +0200
@@ -319,32 +319,38 @@ static inline uint8_t INIT peek_old_byte
}
-static inline void INIT write_byte(struct writer *wr, uint8_t byte)
+static inline int INIT write_byte(struct writer *wr, uint8_t byte)
{
wr->buffer[wr->buffer_pos++] = wr->previous_byte = byte;
if (wr->flush && wr->buffer_pos == wr->header->dict_size) {
wr->buffer_pos = 0;
wr->global_pos += wr->header->dict_size;
- wr->flush((char *)wr->buffer, wr->header->dict_size);
+ if (wr->flush((char *)wr->buffer, wr->header->dict_size)
+ != wr->header->dict_size)
+ return -1;
}
+ return 0;
}
-static inline void INIT copy_byte(struct writer *wr, uint32_t offs)
+static inline int INIT copy_byte(struct writer *wr, uint32_t offs)
{
- write_byte(wr, peek_old_byte(wr, offs));
+ return write_byte(wr, peek_old_byte(wr, offs));
}
-static inline void INIT copy_bytes(struct writer *wr,
+static inline int INIT copy_bytes(struct writer *wr,
uint32_t rep0, int len)
{
do {
- copy_byte(wr, rep0);
+ if (copy_byte(wr, rep0))
+ return -1;
len--;
} while (len != 0 && wr->buffer_pos < wr->header->dst_size);
+
+ return len;
}
-static inline void INIT process_bit0(struct writer *wr, struct rc *rc,
+static inline int INIT process_bit0(struct writer *wr, struct rc *rc,
struct cstate *cst, uint16_t *p,
int pos_state, uint16_t *prob,
int lc, uint32_t literal_pos_mask) {
@@ -378,16 +384,17 @@ static inline void INIT process_bit0(str
uint16_t *prob_lit = prob + mi;
rc_get_bit(rc, prob_lit, &mi);
}
- write_byte(wr, mi);
if (cst->state < 4)
cst->state = 0;
else if (cst->state < 10)
cst->state -= 3;
else
cst->state -= 6;
+
+ return write_byte(wr, mi);
}
-static inline void INIT process_bit1(struct writer *wr, struct rc *rc,
+static inline int INIT process_bit1(struct writer *wr, struct rc *rc,
struct cstate *cst, uint16_t *p,
int pos_state, uint16_t *prob) {
int offset;
@@ -418,8 +425,7 @@ static inline void INIT process_bit1(str
cst->state = cst->state < LZMA_NUM_LIT_STATES ?
9 : 11;
- copy_byte(wr, cst->rep0);
- return;
+ return copy_byte(wr, cst->rep0);
} else {
rc_update_bit_1(rc, prob);
}
@@ -521,12 +527,12 @@ static inline void INIT process_bit1(str
} else
cst->rep0 = pos_slot;
if (++(cst->rep0) == 0)
- return;
+ return 0;
}
len += LZMA_MATCH_MIN_LEN;
- copy_bytes(wr, cst->rep0, len);
+ return copy_bytes(wr, cst->rep0, len);
}
@@ -629,11 +635,17 @@ STATIC inline int INIT unlzma(unsigned c
int pos_state = get_pos(&wr) & pos_state_mask;
uint16_t *prob = p + LZMA_IS_MATCH +
(cst.state << LZMA_NUM_POS_BITS_MAX) + pos_state;
- if (rc_is_bit_0(&rc, prob))
- process_bit0(&wr, &rc, &cst, p, pos_state, prob,
- lc, literal_pos_mask);
- else {
- process_bit1(&wr, &rc, &cst, p, pos_state, prob);
+ if (rc_is_bit_0(&rc, prob)) {
+ if (process_bit0(&wr, &rc, &cst, p, pos_state, prob,
+ lc, literal_pos_mask)) {
+ error("LZMA data is corrupt");
+ goto exit_3;
+ }
+ } else {
+ if (process_bit1(&wr, &rc, &cst, p, pos_state, prob)) {
+ error("LZMA data is corrupt");
+ goto exit_3;
+ }
if (cst.rep0 == 0)
break;
}
@@ -643,9 +655,9 @@ STATIC inline int INIT unlzma(unsigned c
if (posp)
*posp = rc.ptr-rc.buffer;
- if (wr.flush)
- wr.flush(wr.buffer, wr.buffer_pos);
- ret = 0;
+ if (!wr.flush || wr.buffer_pos == 0
+ || wr.flush(wr.buffer, wr.buffer_pos) == wr.buffer_pos)
+ ret = 0;
exit_3:
large_free(p);
exit_2:
--
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