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liblzma: Fix handling of memlimit == 0 in lzma_index_decoder().

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It returned LZMA_PROG_ERROR, which was done to avoid zero as
the limit (because it's a special value elsewhere), but using
LZMA_PROG_ERROR is simply inconvenient and can cause bugs.

The fix/workaround is to treat 0 as if it were 1 byte. It's
effectively the same thing. The only weird consequence is
that then lzma_memlimit_get() will return 1 even when 0 was
specified as the limit.

This fixes a very rare corner case in xz --list where a specific
memory usage limit and a multi-stream file could print the
error message "Internal error (bug)" instead of saying that
the memory usage limit is too low.
This commit is contained in:
Lasse Collin 2017-03-30 18:58:18 +03:00
parent 3d566cd519
commit 5761603265
2 changed files with 13 additions and 9 deletions
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18
src/liblzma/api/lzma/index.h
View file

@ -586,8 +586,7 @@ extern LZMA_API(lzma_index *) lzma_index_dup(
* \param i Pointer to lzma_index which should be encoded.
*
* The valid `action' values for lzma_code() are LZMA_RUN and LZMA_FINISH.
* It is enough to use only one of them (you can choose freely; use LZMA_RUN
* to support liblzma versions older than 5.0.0).
* It is enough to use only one of them (you can choose freely).
*
* \return - LZMA_OK: Initialization succeeded, continue with lzma_code().
* - LZMA_MEM_ERROR
@ -610,16 +609,21 @@ extern LZMA_API(lzma_ret) lzma_index_encoder(
* to a new lzma_index, which the application
* has to later free with lzma_index_end().
* \param memlimit How much memory the resulting lzma_index is
* allowed to require.
* allowed to require. liblzma 5.2.3 and earlier
* don't allow 0 here and return LZMA_PROG_ERROR;
* later versions treat 0 as if 1 had been specified.
*
* The valid `action' values for lzma_code() are LZMA_RUN and LZMA_FINISH.
* It is enough to use only one of them (you can choose freely; use LZMA_RUN
* to support liblzma versions older than 5.0.0).
* Valid `action' arguments to lzma_code() are LZMA_RUN and LZMA_FINISH.
* There is no need to use LZMA_FINISH, but it's allowed because it may
* simplify certain types of applications.
*
* \return - LZMA_OK: Initialization succeeded, continue with lzma_code().
* - LZMA_MEM_ERROR
* - LZMA_MEMLIMIT_ERROR
* - LZMA_PROG_ERROR
*
* liblzma 5.2.3 and older list also LZMA_MEMLIMIT_ERROR here
* but that error code has never been possible from this
* initialization function.
*/
extern LZMA_API(lzma_ret) lzma_index_decoder(
lzma_stream *strm, lzma_index **i, uint64_t memlimit)

4
src/liblzma/common/index_decoder.c
View file

@ -256,7 +256,7 @@ index_decoder_reset(lzma_index_coder *coder, const lzma_allocator *allocator,
// Initialize the rest.
coder->sequence = SEQ_INDICATOR;
coder->memlimit = memlimit;
coder->memlimit = my_max(1, memlimit);
coder->count = 0; // Needs to be initialized due to _memconfig().
coder->pos = 0;
coder->crc32 = 0;
@ -271,7 +271,7 @@ index_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
{
lzma_next_coder_init(&index_decoder_init, next, allocator);
if (i == NULL || memlimit == 0)
if (i == NULL)
return LZMA_PROG_ERROR;
lzma_index_coder *coder = next->coder;