bugGNU Screen - Bugs: bug #46401, Global out of bounds read in...


bug #46401: Global out of bounds read in termcap.c due to wrong loop

Submitted by:  None
Submitted on:  Sun 08 Nov 2015 07:03:44 PM UTC  
Category: Program LogicSeverity: 3 - Normal
Priority: 5 - NormalStatus: None
Privacy: PublicAssigned to: None
Open/Closed: ClosedRelease: None
Fixed Release: NonePlanned Release: None
Work Required: None

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Sun 06 Dec 2015 03:09:38 PM UTC, comment #1:

Thanks for patch!

Pushed to screen-v4 and master.

Amadeusz Sławiński <amade>
Project Administrator
Sun 08 Nov 2015 07:03:44 PM UTC, original submission:

I tested screen with the compiler feature Address Sanitizer (-fsanitize=address in CFLAGS/LDFLAGS). When running screen on a real Linux console (not in an X terminal) it didn't start due to an error.

The error can't be seen directly because screen disables stderr, to reproduce it one can use ASAN_OPTIONS="log_path=[somepath]".

The problem is this code in termcap.c:
s = "l+m+k+j+u+t+v+w+q-x|n+o~s_p\"r#`+a:f'g#~o.v-^+<,>h#I#0#y<z>";
for (i = strlen(s) & ~1; i >= 0; i -= 2)
D_c0_tab[(int)(unsigned char)s[i]] = s[i + 1];

The loop will start right of the string s. One needs to substract 2 from strlen(s) for the code to be correct. Right after that is a loop with the same logic, so the same fix should be applied. I will attached a patch that fixes both.

Will also attach the address sanitizer error message.



(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach File(s):

Attached Files
file #35419:  screen-fix-oob.diff added by None (616B - text/x-patch)
file #35420:  screen-asan-error.10850 added by None (2KiB - application/octet-stream)


Depends on the following items: None found

Items that depend on this one: None found


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    Follow 3 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Sun 06 Dec 2015 03:09:38 PM UTCamadeOpen/ClosedOpen=>Closed
    Sun 08 Nov 2015 07:03:44 PM UTCNoneAttached File-=>Added screen-fix-oob.diff, #35419
      Attached File-=>Added screen-asan-error.10850, #35420

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