edit_dwarf2 calculates the (new) offset in the line program by
taking the difference between the old and new idx, which are of type
size_t (unsigned), plus the size_diff of the header given as ssize_t
(signed), and adding that to the current r_offset, which is an Elf64_Addr
(unsigned). On 64bit architectures, where the size of Elf64_Addr and
ssize_t are the same this isn't a problem. But on 32bit architectures,
where the size of ssize_t is smaller than Elf64_Addr the smaller signed
result gets promoted to an unsigned long first causing issues if the
size_diff was negative.
This would have been caught by gcc -Wsign-conversion
warning: conversion to ‘long unsigned int’ from ‘ssize_t’ {aka ‘long int’}
may change the sign of the result
But enabling this by default gives a lot of false positives.
Found and fixed by Richard Biener <rguent...@suse.de>.
---
tools/debugedit.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/tools/debugedit.c b/tools/debugedit.c
index fa47aa5..e0b1d98 100644
--- a/tools/debugedit.c
+++ b/tools/debugedit.c
@@ -2154,9 +2154,9 @@ edit_dwarf2 (DSO *dso)
/* Offset (pointing into the line program) moves
from old to new index including the header
size diff. */
- r_offset += ((dso->lines.table[lndx].new_idx
- - dso->lines.table[lndx].old_idx)
- + dso->lines.table[lndx].size_diff);
+ r_offset += (ssize_t)((dso->lines.table[lndx].new_idx
+ - dso->lines.table[lndx].old_idx)
+ + dso->lines.table[lndx].size_diff);
if (rtype == SHT_RELA)
{
--
1.8.3.1
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