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IDProjectCategoryView StatusLast Update
0000189file[All Projects] Generalpublic2020-09-05 14:17
ReporternealAssigned Tochristos 
PrioritynormalSeverityminorReproducibilityhave not tried
Status resolvedResolutionfixed 
Product Version 
Target VersionFixed in Version5.40 
Summary0000189: 'use' corrupts 'ms->c'
DescriptionConsider the following magic file:

10 byte x
>&0 byte x 1:%d
>&0 use foo
>&0 byte x 2:%d

20 name foo
>&30 byte x 3:%d

I would expect this to output:

/tmp/byte.bin: 1:11 3:41 2:11

instead, it outputs

/tmp/byte.bin: 1:11 3:41 2:0

Commenting out line 3 ('use foo') causes line 4 to correctly output 2:11.


According to my analysis, this happens, because when mget handles a FILE_USE entry (around line 'softmagic.c:1890') , it recursively calls 'match' with the same magic_set ('ms'). 'match' sets 'cont_level' to 0, and initializes 'ms->c[0]'. Unfortunately, and 'match' doesn't restore it before returning. (In fact, it has to restore the whole continuation level.)

I suspect that the easiest fix would be to turn 'ms->c' into a stack and each time 'match' is used, a new continuation array is pushed. Then before 'match' returns, it pops off the top continuation array.
Steps To Reproduce$ file -d -m /tmp/cont_level.magic /tmp/byte.bin
unknown, 0: Warning: using regular magic file `/tmp/cont_level.magic'
(no description): binary
(no description): text
[try zmagic 0]
[try tar 0]
[try json 0]
[try cdf 0]
[try elf 0]
bb=[0x7f1ab5c42010,256], 10 [b=0x7f1ab5c42010,256], [o=0xa, c=0]
mget(type=1, flag=0x20, offset=10, o=0, nbytes=256, il=0, nc=0)
mget/96 @10: \n\v\f\r\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037 !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghi

1: > 10 byte&,x,""]
10 == *any* = 1
bb=[0x7f1ab5c42010,256], 0 [b=0x7f1ab5c42010,256], [o=0, c=1]
mget(type=1, flag=0x2, offset=11, o=0, nbytes=256, il=0, nc=0)
mget/96 @11: \v\f\r\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037 !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghij

2: >> 0 byte&,x,"1:%d"]
11 == *any* = 1
bb=[0x7f1ab5c42010,256], 0 [b=0x7f1ab5c42010,256], [o=0, c=1]
mget(type=46, flag=0x2, offset=11, o=0, nbytes=256, il=0, nc=0)
mget/96 @11: \v\f\r\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037 !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghij

3: >> 0 use,='foo',""]
bb=[0x7f1ab5c42010,256], 20 [b=0x7f1ab5c42010,256], [o=0x14, c=0]
mget(type=45, flag=0, offset=20, o=11, nbytes=256, il=0, nc=1)
mget/96 @20: \037 !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~

6: > 20 name,='foo',""]
bb=[0x7f1ab5c42010,256], 30 [b=0x7f1ab5c42010,256], [o=0x1e, c=1]
mget(type=1, flag=0x2, offset=30, o=11, nbytes=256, il=0, nc=1)
mget/96 @30: )*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~\177\200\201\202\203\204\205\206\207\210

7: >> 30 byte&,x,"3:%d"]
41 == *any* = 1
bb=[0x7f1ab5c42010,256], 0 [b=0x7f1ab5c42010,256], [o=0, c=1]
mget(type=1, flag=0x2, offset=0, o=0, nbytes=256, il=0, nc=0)
mget/96 @0: \000\001\002\003\004\005\006\a\b\t\n\v\f\r\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037 !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_

4: >> 0 byte&,x,"2:%d"]
0 == *any* = 1
[try softmagic 1]
/tmp/byte.bin: 1:11 3:41 2:0
TagsNo tags attached.

Activities

neal

2020-08-26 10:44

reporter  

byte.bin (256 bytes)
cont_level.magic (84 bytes)

christos

2020-09-05 14:17

manager   ~0003473

Nice catch! Thanks.

Issue History

Date Modified Username Field Change
2020-08-26 10:44 neal New Issue
2020-08-26 10:44 neal File Added: cont_level.magic
2020-08-26 10:44 neal File Added: byte.bin
2020-09-05 14:16 christos Assigned To => christos
2020-09-05 14:16 christos Status new => assigned
2020-09-05 14:17 christos Status assigned => resolved
2020-09-05 14:17 christos Resolution open => fixed
2020-09-05 14:17 christos Fixed in Version => 5.40
2020-09-05 14:17 christos Note Added: 0003473