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nftw: fix use of uninitialized struct stat 

If lstat/stat fails with EACCES, st is left uninitialized, but its
st_dev/st_ino fields are then used in several places:

* for FTW_MOUNT check (in practice typically results in a false
  positive and an early return)
* for copying to the new struct history (though the struct is not used
  afterwards since we don't recurse in this case)
* for cycle detection check (could theoretically result in a false
  positive and an early return)

To avoid adding FTW_NS checks to all these places, fix this by
zero-initializing st_dev/st_ino (which can never match an existing
dentry due to zero inode being reserved in Linux), and check for FTW_NS
only when handling FTW_MOUNT since we need two valid dentries there.
This commit is contained in:
Alexey Izbyshev 2023-03-10 17:00:50 +03:00 committed by Rich Felker
parent 7c41047285
commit 35e9831156
1 changed files with 3 additions and 1 deletions
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4
src/misc/nftw.c
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@ -31,6 +31,8 @@ static int do_nftw(char *path, int (*fn)(const char *, const struct stat *, int,
int err;
struct FTW lev;
st.st_dev = st.st_ino = 0;
if ((flags & FTW_PHYS) ? lstat(path, &st) : stat(path, &st) < 0) {
if (!(flags & FTW_PHYS) && errno==ENOENT && !lstat(path, &st))
type = FTW_SLN;
@ -46,7 +48,7 @@ static int do_nftw(char *path, int (*fn)(const char *, const struct stat *, int,
type = FTW_F;
}
if ((flags & FTW_MOUNT) && h && st.st_dev != h->dev)
if ((flags & FTW_MOUNT) && h && type != FTW_NS && st.st_dev != h->dev)
return 0;
new.chain = h;