Decompressors: check for write errors in decompress_unlzma.c

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().

Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alain Knaff <alain@knaff.lu>
Cc: Albin Tonnerre <albin.tonnerre@free-electrons.com>
Cc: Phillip Lougher <phillip@lougher.demon.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 32 insertions, 21 deletions

diff --git a/lib/decompress_unlzma.c b/lib/decompress_unlzma.c
index 4281aa9cb76c..f30c899241ef 100644
--- a/lib/decompress_unlzma.c
+++ b/lib/decompress_unlzma.c
@@ -313,32 +313,38 @@ static inline uint8_t INIT peek_old_byte(struct writer *wr,
 
 }
 
-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) {
@@ -372,16 +378,17 @@ static inline void INIT process_bit0(struct writer *wr, struct rc *rc,
                 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;
@@ -412,8 +419,7 @@ static inline void INIT process_bit1(struct writer *wr, struct rc *rc,
 
                                 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);
                         }
@@ -515,12 +521,12 @@ static inline void INIT process_bit1(struct writer *wr, struct rc *rc,
                 } 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);
 }
 
 
@@ -623,11 +629,17 @@ STATIC inline int INIT unlzma(unsigned char *buf, int in_len,
                 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;
                 }
@@ -637,9 +649,8 @@ STATIC inline int INIT unlzma(unsigned char *buf, int in_len,
 
         if (posp)
                 *posp = rc.ptr-rc.buffer;
-        if (wr.flush)
-                wr.flush(wr.buffer, wr.buffer_pos);
-        ret = 0;
+        if (!wr.flush || wr.flush(wr.buffer, wr.buffer_pos) == wr.buffer_pos)
+                ret = 0;
 exit_3:
         large_free(p);
 exit_2: